Semiconductor Physics

for an Invited Paper for the MAR12 Meeting of the American Physical Society Electrical characterization of interfacial defects GENNADI BERSUKER, SEMATECH Aggressive transistor scaling to achieve better chip functionality calls for the introduction of new dielectric and metal materials into traditional device gate stacks. The advanced gate stacks represent multilayer structures, the materials of which may strongly interact (primarily during high temperature processing), generating structural defects in these layers. These complex structures pose new challenges in interpreting electrical measurements, which are sensitive to even extremely small concentrations of electrically active defects. The critical task is, thus, to link the structural and electrical characteristics of these multicomponent gate stacks in order to identify and control defects affecting device performance. In this presentation, we focus on analyzing interfacial defects affecting electrical characteristics of the metal/high-k (HK) gate stacks, which are of major interest to the semiconductor industry. We first developed models of the physical processes governing the measurements of the electrical techniques we used that allowed us to extract the structural parameters of the defects from the electrical data. By comparing the extracted parameters to those obtained by ab initio calculations of the material structures, we identified the nature of the contributing defects. A recently proposed model for random telegraph noise (RTN) and frequency-dependent charge pumping (CP) measurements that takes into consideration the multi-phonon lattice relaxation induced by charge trapping/detrapping at the defect sites was employed to extract characteristics of the traps in the interfacial SiO2 layer in HfO2-based HK devices. Our results indicate that the electron capture/emission times are controlled by the lattice re-arrangement (caused by the trapped electrons) rather than by electron tunneling to/from the trap as generally assumed. The strong dependency of the measured values on defect relaxation and ionization energies allows these values to be extracted; the values can then be used as a defect identifier. Complementary modeling of the gate leakage current in HK devices during electrical stress using the same approach yields characteristics of the traps in the interfacial SiO2 layer contributing to trap-assisted tunneling (TAT). Based on the values obtained by RTN, CP, and TAT measurements, the electrically active defects were tentatively assigned to oxygen vacancies in various charged states. In all cases, stress-induced traps were generated exclusively in the interfacial layer of the HK stacks, consistent with earlier findings that HK dielectrics are more resistant to defect generation than SiO2. Based on these findings, as well as an earlier TEM/EELS study of the elemental composition of the breakdown path, we proposed that the breakdown path formation/evolution in the interfacial layer is associated with the growth of an oxygen-deficient filament facilitated by the grain boundaries in the overlaying high-k film. This model successfully describes the temperature-dependent evolution of interfacial layer degradation through various breakdown phases.

We have modeled diffusion of H in a two-step Si 3 N 4 passivation process invoking the concept of "storage" of H. The H stored during nitridation is redistributed during a subsequent anneal. The modeling results agree with this hypothesis, and the conclusions also appear to concur with the observations

Nanomaterial, dengan ukuran dalam rentang nanometer, telah menarik perhatian luas dalam beberapa dekade terakhir karena sifat-sifatnya yang unik dan potensial untuk aplikasi yang luas. Salah satu aspek penting dari nanomaterial adalah sifat listriknya yang dapat berbeda secara signifikan dari materi bulk. Saat ukuran partikel menyusut menjadi skala nanometer, properti listrik dapat mengalami perubahan dramatis karena efek kuantum dan permukaan yang dominan pada skala tersebut. Dalam konteks ini, pemahaman tentang sifat listrik nanomaterial menjadi kunci untuk pengembangan teknologi baru yang mencakup sensor, komponen elektronik, baterai, dan berbagai aplikasi nanoelektronika lainnya. Perubahan sifat listrik pada nanomaterial terutama disebabkan oleh dua faktor utama, yaitu efek kuantum dan efek permukaan. Efek kuantum mengacu pada fenomena di mana sifat-sifat elektron dalam materi berubah secara signifikan karena ukuran partikel menyusut menjadi skala nanometer. Misalnya, pada ukuran nanometer, elektron dalam nanomaterial dapat terlokalisasi, menyebabkan perubahan dalam konduktivitas listrik dan sifat optik. Selain itu, efek permukaan menjadi lebih signifikan pada nanomaterial karena perbandingan luas permukaan terhadap volume yang jauh lebih tinggi dibandingkan dengan materi bulk. Ini dapat menghasilkan efek seperti peningkatan konduktivitas, kapasitansi, dan kemampuan reaksi kimia di permukaan nanomaterial.

In photonic crystals made of materials with a frequency dependent dielectric function surface plasmon modes are extending over some adjacent layers and it turns out, that the dispersion can be tailored by coupling surface plasmons of adjacent layers. To give a detailed study we start investigating surface plasmons on a single metallic sheet. The mode dispersion is not bijective any more (i.e. is bent back) due to the coupling of surface plasmons and radiative modes, and the group velocity diverges and is even negative. This effect is still physical as the absorption of the metal influences the properties of the surface plasmons and yields an inequality between group and energy velocity. Next to these effects we investigate the propagation distance of the surface states and optimize them by varying the thickness of the layers. Finally we calculate the dispersion for two adjacent layers to see possible coupling effects.

Crystallinity, optical band gap, resistivity and photoresponse of thermally evaporated In 2 S 3 thin films deposited at a temperature of 350 • C and further annealed in sulfur vapour at different temperature range of 200-300 • C is investigated. It is observed that with an increase of annealing temperature, predominantly β-In 2 S 3 phase is formed and the optical band gap for indirect allowed transitions increases from 1.6 eV to 2.0 eV and for direct allowed transitions from 2.3 eV to 2.7 eV. The electrophysical properties indicate that the activation mechanism of conductivity with an activation energy in the range of 0.5-0.73 eV, which is typical for the presence of indium vacancies in the β-In 2 S 3 crystal structure and for the replacement of sulfur by oxygen atoms. It is also noted that sulfur annealing at temperatures of 250-300 • C leads to an increase in the conductivity and photosensitivity of films, which is suitable for photovoltaic applications.

Tin sulfoselenide (SnS 1-x Se x ) is a novel ternary semiconductor that belongs to the IV -VI group of compounds. It possesses the properties of both SnS and SnSe, which are proved as good absorber materials for solar cell fabrication. In the present work, SnS 0.7 Se 0.3 thin films were deposited by vacuum co-evaporation technique at four different substrate temperatures (T s ), 200 °C, 250 °C, 300 °C and 350 °C. The optical properties of as-deposited SnS 0.7 Se 0.3 films were analyzed using optical measurements. From the optical transmittance and reflectance data, the band gap energy of the layers was determined that varied in the range, 1.59-1.46 eV. The other optical parameters such as skin depth, refractive index, extinction coefficient, optical conductivity and dielectric constant of SnS 0.7 Se 0.3 layers were determined and discussed as a function of substrate temperature. Moreover, the dispersion parameters of the layers were also evaluated using Wemple -DiDomenico (WDD) single oscillator model. The dispersion energy (E d ) and oscillator energy (Ε o ) of the films were evaluated and varied in the range, 2.19-2.38 eV and 7.55-9.52 eV respectively. Moreover, the optical dispersion moments (M À1 and M À3 ) were also calculated that were varied from 0.25 to 0.29 and from 2.76 Â 10 -3 to 5.08 Â 10 -3 respectively.

The structural, compositional, morphological and optical properties of In 2 S 3 thin films, prepared by thermal evaporation technique and annealed in sulfur ambient at different temperatures have been investigated. The grazing incident X-ray diffraction patterns have indicated polycrystalline form and predominantly cubic structure of annealed In 2 S 3 films. The scanning electron microscopy revealed textured surface with uniformly distributed grains and the grain size increased with increase of annealing temperature. The optical parameters of the films have been determined using conventional transmission and reflection spectra as well as from surface photovoltage measurements.

Indium sulfide (In2S3) is a wide bandgap semiconductor, which is widely used as a window/buffer layer in thin film solar cell applications. In2S3 thin films were deposited using thermal evaporation technique and were annealed in sulfur ambient at 200 °C and 250 °C. Further, these films were treated in inductively coupled argon plasma sputtering with an average argon ion energy of 75 eV for 30 s. The paper presents the effect of Ar-plasma treatment on structure, elemental composition, morphology and topography of In2S3 films and the results were reported. Further, the optimized In2S3 layers were continued for plasma etching process with an average argon ion energy of 25 eV to study the effect of plasma etching duration on the growth of metallic indium nanoparticles over the film surface and the results were discussed in detail.

In this paper, we study the process of growth from the melt by Chokhralsky method of bulk β-Ga2O3 crystals. The effect of different configurations of growth zones and ambient composition on resulting bulk crystal quality has been evaluated. It is shown that the vertical gradient has a great influence on the quality of the growing crystal and the stability of growth. The optical properties of obtained β-Ga2O3 crystals were investigated. The crystallographic orientation of crystal faces and the structural quality of the samples were studied with the use of XRD.

The article presents the results of the study of the mechanical properties and defect structure of gallium oxide (Ga2O3) by using the piezoelectric composite oscillator technique. Bulk samples of the Ga2O3 beta phase in the form of single crystals and their intergrowths were obtained by growth from a melt with a shaper (Stepanov technique). The research involved studying the dependences of the longitudinal elastic modulus and the damping of elastic vibrations at a frequency of 100 kHz on the strain amplitude. Changes in the elastic and microplastic properties of the samples at different temperatures were attributed to possible relaxation phenomena in the structure of the material. Studying the defect structure in samples of pure and doped Ga2O3 is necessary to improve the technology for the production of large single crystals. The fundamental questions in this area are the influence of defects on the anisotropy of electrical conductivity, band structure, and other functional properties of the resulting semiconductor material. The purpose of this article is to establish the features of sample preparation, research, and interpretation of the results obtained by the piezoelectric composite oscillator technique for gallium oxide samples. In the studied samples, the first longitudinal vibration mode was excited, which corresponded to a length of about 27 mm and a small cross-section of the sample. The temperature dependences in the region of low and high strain amplitudes were determined separately. The crystalline quality of the prepared samples was assessed by X-ray diffraction with the analysis of the rocking curve. The value of Young's modulus obtained along the growth axis (crystalline orientation <010>) in Ga 2 O 3 crystals E≈260 GPa is in line with the results of previous studies. Relaxation peaks corresponding to various dislocation interactions were found on the temperature dependences of internal friction at a temperature of 280 K.

Results of successful experiments on the growth of gallium oxide (β-Ga 2 O 3) crystals by the Czochralski method are reported. The influence of growth atmosphere on the crystalline perfection of obtained material has been studied. It established that high-quality transparent optical crystals can be obtained provided the atmosphere contains about 5 vol % oxygen. As-grown β-Ga 2 O 3 crystals were characterized by X-ray diffraction and optical transmission measurements.

The aluminum distribution in the surface layer of an (Al x Ga 1-x) 2 O 3 crystal grown on a sapphire seed by the Czochralski method has been studied using X-ray fluorescence and X-ray diffraction mapping and scanning electron microscopy. It is shown that the aluminum distribution correlates with a change in the physical broadening of the diffraction maxima of the (h00) plane system of the crystal and is related to a distance from the seeding zone.

A method is proposed for increasing the radiation resistance of semiconductor crystals (Al x Ga 1-x) 2 O 3 , which are promising for creating power electronics and optoelectronic devices for spacecraft performing tasks in near-earth orbits. The effect of the aluminum content on the bandgap in (Al x Ga 1-x) 2 O 3 single crystals grown from a melt by the Czochralski method is investigated. The necessary conditions for the formation of a high-quality seed and subsequent growth of single crystals are achieved by setting temperature gradients at each successive stage of growth. The results of energy-dispersive X-ray spectroscopy analysis and optical transmission spectra of (Al x Ga 1-x) 2 O 3 crystals with an aluminum content from 0 to 7.32% are presented. It is shown that an increase in the aluminum content leads to a monotonic increase in the bandgap from 4.7 eV to 5.0 eV, which provides an increase in radiation resistance.

Bulk β-Ga 2 O 3 samples grown by the Czochralski method are studied. Based on the studies of the absorbed current dynamics and the cathodoluminescence, it is shown that there is a localization of charges of both signs in the sample. The electron localization is demonstrated to lead to a substantial decrease in cathodoluminescence intensity.

The present work is focussed on Zinc (2, 4, 6, 8 and 10 wt%) doped CdS thin films synthesized by sol-gel spin coating method and deposited on glass substrates. X-ray diffraction patterns of Zn doped CdS thin films exhibit cubic structure. The microstructural properties such as crystallite size, lattice constant, microstrain, dislocation density and stacking fault probability in the films were reported. The surface morphology and topography of the films was studied by using field emission scanning electron microscopy and atomic force microscopy. The incorporation of Zn in CdS and elemental composition of the films has been confirmed with X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). Raman spectrum of Zn doped CdS thin films exhibits 1LO and 2LO phonon modes. The optical band gap of CdS thin films increased from 2.63 to 2.73 eV with the increase of Zn dopant from 2 to 10%. Thermoelectric power measurements show negative Seebeck coefficient indicating n-type semiconducting behaviour. The carrier concentration of Zn doped CdS thin films at room temperature are found to be in the range of 10 19-10 20 cm-3 suggesting that the prepared films are degenerate semiconductors. The increase in thermal conductivity of Zn doped CdS thin film is due to the increase in carrier concentration of the films. The lattice thermal conductivity of Zn doped CdS thin films had an inverse temperature dependent and at high temperatures shows the dominance of phonon scattering.

It is known that the thermal efficiency of materials is directly proportional to the product of the electrical conductivity multiplied by the thermo-electromotive force squared and inversely proportional to the thermal conductivity. To search for new materials with high thermal efficiency, the author was interested in calculating the influence of the effect of electron drag by phonons on the thermo-electromotive force in the case where small dimensions affect the properties of known materials (the author chose Ge, but another material could have been chosen, such as Silicon or Graphite). To reduce the size of materials, a one-dimensional system in the form of a thread (quantum wire) was chosen. As a result, it was shown that due to a decrease in the transverse size of the wire, the thermo-electric force in it increased by two orders of magnitude, which is important for increasing the thermal efficiency of materials.

The self-heating effect of the silicon-on-insulator (SOI)-raised-buried-oxide (RBOX) ferroelectric tunnel field effect transistor is explored in this article. Proposed device reliability issues have been examined by activating the acceptor and donor uniform and Gaussian interface trap concentrations (ITCs). The proposed TFET is designed to diminish the ambipolar current, intensify on-state current and to improve subthreshold slope. The device performance for Analog/RF applicability is also tested by calculating the capacitances (Cgg-3.6 × 10-16 F/µm), transconductance in the order of 7.3 × 10-3 S/µm, the cutoff frequency of 71 THz, and further transistor frequency product of 3.1 × 10 15 Hz/V, transit time (1.4 × 10-15 s), and gain-bandwidth product of 12 THz are determined. All these parameter variations are investigated by changing the temperature and trap concentrations. The parameters have been compared with the room temperature and noticed an improved performance in terms of Analog/RF applicability. In addition, the introduction of the trap concentrations at the interfaces such as front gate oxide/silicon and the silicon/buried oxide is compared with no trap concentrations. It is proven that for Analog/RF applications, the proposed SOI-RBOX-ferroelectric-TFET exhibits the prominent behavior.

Here, the proposed device is a negative capacitance based ferroelectric gate stack, raised buried oxide pocket doped SOI TFET (RBOX-SOI-Fe TFET). The architecture of the device is carefully designed with proper optimization of the pocket and ferroelectric thickness to boost the on-state current, on-off current ratio, and to improve subthreshold swing. At, first the polarization versus electric field curve of the proposed device is studied. Next, the DC and the analog/RF, linearity performance analysis are illustrated. The various analog/RF performance parameters like gate-to-source capacitance (Cgs-1.7 × 10-16 F/µm), gate-to-drain capacitance (Cgd-2.3 × 10-17 F/µm), total capacitance (Cgg-1.96 × 10-16 F/µm), transconductance (7.35 × 10-3 S/µm), output conductance, corner frequency (7.1 × 10 13 Hz), the gain bandwidth product (1.2 × 10 13 Hz), transit time (1.4 × 10-15 s), transistor frequency product (3.1 × 10 15 Hz/V), and intrinsic gain (6.91 × 10 3) have been investigated. The proposed device parameters have been compared with the existing devices in literature and RBOX-SOI-Fe TFET evinces an improved result in terms of both DC and Analog/RF parameters. Device simulations have been performed by Sentaurus TCAD 2D-simulator.

Zinc-cobalt sulphide (Zn x Co 1Àx S) thin films were fabricated on glass substrates using the chemical bath deposition (CBD) technique. In this study, the films were grown employing solutions of zinc acetate, cobalt sulphate, and thioacetamide as the respective sources of zinc, cobalt, and sulphur. The synthesized films were investigated for their potential use in optoelectronic device applications. Optical characterization revealed that the films exhibited a direct transition with an energy gap ranging from 3.350 to 3.360 eV. As the zinc concentrations were changing, the absorbance of the films were decreasing uniformly along the wavelength spectra. The films exhibit a low extinction coefficient (0.0-0.23) that may be due to the internal reflections within the material as concentrations changes. Variations in the thickness, reflectance and refractive index with zinc concentrations were also discussed. The electrical resistivity was found to decrease from 7:12 Â 10 8 to 5:94 Â 10 8 (Ω.cm) with zinc concentrations. According to the crystallography spectrum, Zn x Co 1Àx S has a polycrystalline structure with various distinct peaks at different orientations. Scanning electron microscopy shows that surface morphology of Zn x Co 1Àx S films has a well-defined nanoparticles of different shapes and sizes which are uniformly distributed and are significantly transformed as a function of concentrations. The results demonstrate that the chemically deposited thin films can be engineered for a range of optoelectronic applications.

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to the Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 2. REPORT TYPE 3. DATES COVERED (From -To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 6. AUTHOR(S) 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) 11. SPONSOR/MONITOR'S REPORT NUMBER(S)

Gallium nitride pin rectifiers grown on bulk GaN substrate have been fabricated and characterised. The device structures were grown by metal organic chemical vapour deposition (MOCVD) on free-standing GaN substrates. The diode structure consisted of an n þ -GaN layer, followed by a 2.5 mm unintentionally doped i-GaN layer, and a p-type GaN layer capped with a p þþ -GaN cap layer. The mesa-structure pin diodes exhibited a blocking voltage as large as V r $À540 V, and a reverse current density of I r $0.1 A=cm 2 at V r $À500 V. The forward voltage drop is only 4.4 V at a forward current density of $100A=cm 2 , with an on-resistance of 3 mO Á cm 2 for a circular device with an 80 mm mesa diameter. The breakdown voltage and on-resistance are believed to be the best values reported for vertical mesa GaN pin rectifiers grown on bulk GaN substrates with comparable i-layer thickness.

An approach using a differential evolution (DE) optimization algorithm is proposed to optimize design parameters for improving the optical absorption efficiency of plasmonic solar cells (PSC). This approach is based on formulating the parameters extraction as a search and optimization process in order to maximize the optical absorption in the PSC. Determining the physical parameters of three-dimensional (3-D) PSC is critical for designing and estimating their performance, however, due to the complex design of the PSC, parameters extraction is time and calculation intensive. In this paper, this technique is demonstrated for the case of commercial thin-film hydrogenated amorphous silicon (a-Si:H) solar photovoltaic cells enhanced through patterned silver nano-disk plasmonic structures. The DE optimization of PSC structures was performed to execute a real-time parameter search and optimization. The predicted optical enhancement (OE) in optical absorption in the active layer of the PSC ...

The integration of AI and machine learning in precision mechanical systems has significantly transformed semiconductor lithography, enabling higher accuracy, enhanced system reliability, and optimized operational efficiency. This study investigates the impact of AI-driven approaches on predictive maintenance, adaptive error compensation, motion control, metrology accuracy, and thermal management, focusing on their role in improving lithographic performance and process stability. Through a comprehensive review of 50 research papers and 10 industry case studies, this study evaluates how machine learning algorithms enhance predictive maintenance strategies, reducing unplanned downtime by 40%, while adaptive learning models improve motion accuracy by 35%, mitigating thermal drift and stage hysteresis. AI-enhanced motion control strategies have increased production efficiency by 30%, optimizing trajectory planning and resonance damping, whereas AI-powered metrology systems have improved overlay correction by 35% and defect detection by 50%, ensuring higher yield rates and reduced process variability. Additionally, AI-driven thermal modeling and real-time calibration techniques have led to a 40% improvement in system stability, enhancing heat dissipation and mechanical longevity. These findings confirm that AI-enabled precision mechanical systems are critical in advancing next-generation semiconductor lithography, offering higher throughput, improved defect control, and greater process repeatability. The insights gained from this study provide a foundation for future innovations in AI-driven automation, ensuring that semiconductor manufacturing continues to meet the demands of nanometer-scale fabrication with increased efficiency and reliability.

Electronic structure and vibrational characteristics of GaAlN wurtzoids at the molecular-nanoscale limit are investigated. The investigated properties include energy gap, vibrational properties, and phase stability against transition to GaAlN diamondoids. At the molecular-nanoscale limit, wurtzite GaAlN nanocrystals are represented by wurtzoids. The properties of GaAlN molecules and nanocrystals as a function of Ga and Al contents are shown. The results show that the energy gap depends on size, shape and surface conditions. Molecules with hydrogen passivated surface have wide energy gap while bare molecules have smaller energy gaps. On the other hand, vibrational longitudinal optical mode of bare molecules experiences a redshift after surface hydrogen passivation with smaller vibrational reduced masses and force constant at a given frequency. Differences between GaAlN two limits (GaN and AlN) are explained by the existence of d orbitals in Ga atoms. Calculated Gibbs free energy of atomization show the stability of wurtzoids against transition to the diamondoids at the molecular-nanoscale limit for both bare and hydrogen passivated cases.

This research aims to study the growth of TiO2 under a direct imposition of a strong permanent neodymium magnet with a magnetic dipole. The objective of the research is to study the effect of the magnetic field imposition on the growth and characterisation of TiO2. Methodically, this research uses ammonium fluoride as the electrolyte and platinum as the cathode. The characterisation encompasses the I-t curve, annealing, FESEM, and XRD. The research discovered that only the perpendicular magnet imposition has the electromagnetic effect on the anions. The research also found that the magnetic field imposition catalyses the formation of the rutile phase at 450°C, and more rutile phase formations are observed under the magnetic field imposition at 650°C. The interplanar distance increases under the magnetic field imposition, but the FWHM fails to show a consistent trend. The I-t curves of the region A-B for the parallel magnet imposition do have a lower anodizing current due to the interference of the diamagnetism effect. As for the perpendicular magnet imposition, the lower anodizing current due to the interference of the diamagnetism effect and the Lorentz force is observed with a poor oxide formation due to the separation of ions. As for the region B-C for the parallel magnet imposition, the diamagnetism effect interferes the oxide pits formation causing the lower anodizing current. As for the perpendicular magnet imposition, the lower anodizing current due to the interference is observed with a localised F- concentration. The TiO2 microscopy discovered that all the magnetic field impositions—except for the perpendicular-north magnet imposition—yields larger TiO2 nanotubes but a less dense TiO2 thin film.

Quantum dot-sensitised solar cells (QDSSCs) have turned out to be strong alternatives in comparison to conventional solar cell technology, with important advantages like reduced environmental impact and cost. QDSSCs generate more electrons at the electrolyte interface than dye-sensitised solar cells (DSSCs) in order to increase efficiency. With the replacement of 𝑇𝑖𝑂2 with 𝑍𝑛𝑂, an increase in performance can be achieved. Synthesis methods for quantum dots include colloidal synthesis, hydrothermal synthesis, and biomimetic synthesis. Colloidal synthesis is the process by which metal ions are dissolved in a solvent. Hydrothermal synthesis is a high-pressure and high-temperature process. Biomimetic synthesis is a biological nucleation process. The advantages of ZnO quantum dots are mainly due to their quantum confinement effect, which causes the large exciton binding energy. By selecting a suitable synthesis method and material, the efficiencies of the solar cells can be significantly improved.

Traditionally, digital imaging systems rely on the use of dedicated photodetectors to capture specific wavelengths in the visible spectrum. These photodetectors, which are commonly made of silicon, are arranged as arrays to capture the red, green and blue wavelengths. The signal captured by the individual photodetectors must then be interpolated and integrated to obtain the closest color match and the finest possible resolution with reference to the actual object. The use of spatially separated detectors to sense primary colors reduces the resolution by a factor of three compared to black and white imaging. The FOVEON detector technology greatly improves the color and resolution of the image through its vertically arranged, triple well photodetector. This is achieved by exploiting the variation of absorption coefficient of silicon with wavelength in the visible spectrum. Hence, in a silicon detector, the shorter wavelength (e.g. blue) would be mainly absorbed at a shallow depth. A longer wavelength (e.g. red) would penetrate the material deeper than the shorter wavelengths and be primarily absorbed at a greater depth. By producing a layered silicon detector, all three primary colour wavelengths of red, green and blue can be captured simultaneously. This thesis aims to study the FOVEON camera’s ability to image light from the near Infrared (NIR) to the Ultra-Violet (UV) range of the electromagnetic spectrum. The imaged obtained using a set of bandpass filters show that the camera has response both in the UV as well as NIR regions.

Optical and light emitting diode structures with an active InGaN region containing short period InGaN/GaN superlattices are studied. It is shown that short period superlattices are thin two dimensional layers with a relatively low In content that contain inclusions with a high In content 1-3 nm thick. Inclusions manifest themselves from the point of view of optical properties as a nonuniform array of quantum dots involved in a residual quantum well. The use of short period superlattices in light emitting diode structures allows one to decrease the concentration of nonradiative centers, as well as to increase the injection of carriers in the active region due to an increase in the effective height of the AlGaN barrier, which in general leads to an increase in the quantum efficiency of light emitting diodes.

We report on the electrical properties of the AlN/4H-SiC interface using capacitance-and conductance-voltage (CV and GV) analysis of AlN/SiC MIS capacitors. The crystalline AlN layers are made by hot wall MOCVD. CV analysis at room temperature reveals an order of magnitude lower density of interface traps at the AlN/SiC interface than at nitrided SiO 2 /SiC interfaces. Electron trapping in bulk traps within the AlN is significant when the MIS capacitors are biased into accumulation resulting in a large flatband voltage shift towards higher gate voltage. This process is reversible and the electrons are fully released from the AlN layer if depletion bias is applied at elevated temperatures. Current-voltage (IV) analysis reveals that the breakdown electric field intensity across the AlN dielectric is 3-4 MV/cm and is limited by trap assisted leakage. By depositing an additional SiO 2 layer on top of the AlN layer, it is possible to increase the breakdown voltage of the MIS capacitors significantly without having much impact on the quality of the AlN/SiC interface.

We have calculated the plasmon frequency of the two-dimensional electron gas (2DEG) in AlGaN/GaN high electron mobility transistors (HEMT). The impact of HEMT&#39;s parameters on the plasmon frequency and the sheet charge density of the 2DEG is discussed in detail. The charge density in the HEMT&#39;s channel is calculated by means of a triangular quantum well model. It has been found that the AlGaN/GaN heterostructure induces plasmon oscillations in the THz range with larger frequencies compared with other semiconductor compounds. The sensitivity of the tunability of these frequencies is considerable, especially using a variable applied gate voltage. We have derived optimal structure parameters for obtaining a maximum plasmon frequency for a given doping concentration. We will show that the accuracy of this optimized frequency value is dependent on the average position Δd of charge density in the triangular shaped (quantum well) channel. The interaction between radiation and plasmo...

In evaluating GaN HEMTs for high-power applications, it is crucial to consider the device-level breakdown characteristics. This work replaces the conventional AlGaN barrier and common AlGaN backbarrier with unstrained AlN, and it assesses the breakdown voltage of AlN/GaN/AlN quantum well HEMTs for gate-drain spacings in the range of 0.27 to 5.1 microns. Results are highlighted by a high breakdown voltage of 78 V for a gate-drain spacing of 390 nm, among the best reported for submicron-channel devices. Additionally, small-signal RF measurements showed record performance for HEMTs on the AlN platform, with ft/fmax = 161/70 GHz. Cutoff frequency and corresponding drain bias are benchmarked against stateof-the-art GaN HEMTs using the Johnson figure of merit, with measured devices highlighted by a JFoM value of 2.2 THz•V. These results illustrate the potential for AlN/GaN/AlN quantum well HEMTs as a future platform for high-power RF transistors.

Epitaxy is a process by which a thin layer of one crystal is deposited in an ordered fashion onto a substrate crystal. The direct epitaxial growth of semiconductor heterostructures on top of crystalline superconductors has proved challenging. Here, however, we report the successful use of molecular beam epitaxy to grow and integrate niobium nitride (NbN)-based superconductors with the wide-bandgap family of semiconductors-silicon carbide, gallium nitride (GaN) and aluminium gallium nitride (AlGaN). We apply molecular beam epitaxy to grow an AlGaN/GaN quantum-well heterostructure directly on top of an ultrathin crystalline NbN superconductor. The resulting high-mobility, two-dimensional electron gas in the semiconductor exhibits quantum oscillations, and thus enables a semiconductor transistor-an electronic gain element-to be grown and fabricated directly on a crystalline superconductor. Using the epitaxial superconductor as the source load of the transistor, we observe in the transi...

Undoped AlN/GaN heterostructures, grown on sapphire by molecular beam epitaxy, exhibit very low sheet resistances, ~ 150 Ohm/sq, resulting from the 2-dimensional electron gas situated underneath a 4 nm thin AlN barrier. This extraordinarily low sheet resistance is a result of high carrier mobility and concentration (~ 1200 cm 2 /Vs and ~ 3.5x10 13 cm -2 at room temperature), which is ~ 3 x smaller than that of the conventional AlGaN/GaN heterojunction field effect transistor (HFET) structures. Using a 5 nm SiN x deposited by plasma enhanced chemical vapor deposition as gate-dielectric, HFETs were fabricated using these all binary AlN/GaN heterostructures and the gate tunneling current was found to be efficiently suppressed. Output current densities of 1.7 A/mm and 2.1 A/mm, intrinsic transconductance of 455 mS/mm and 785 mS/mm, were achieved for 2 µm and 250 nm gate-length devices, respectively. Current gain cut-off frequency f T of 3.5 GHz and 60 GHz were measured on 2 µm and 250 nm gate-length devices, limited by the high ohmic contact resistance as well as the relatively long gate length in comparison to the electron mean free path under high electric fields.

Unlike silicon and traditional III-V semiconductors, the III-nitrides exhibit high spontaneous and piezoelectric polarization charges at epitaxial polar heterojunctions. In the process of investigating scaling properties of gate-stacks consisting atomic-layer deposited Al2O3/III-Nitride heterojunctions, we find interface charges that appear closely linked to the polarization charges of the underlying nitride substrate. Through capacitance-voltage measurement on a series of samples of varying dielectric thicknesses, we find the presence and propose an origin of benign donor-type interface charges (Qit ∼6 × 1013 cm−2) at the AlN/Al2O3 junction. This interface charge is almost equal to the net polarization charge in AlN. The polarization-related dielectric/AlN interface charge and the role of oxygen in the dielectric as a possible modulation dopant potentially offer opportunities for various device applications.

Mn ions in (Ga,Mn)N exhibit a tendency to form pairs, which is enhanced by ferromagnetic Mn–Mn coupling. We also find that segregation of Mn to form MnN clusters in the wurtzite structure of host GaN is energetically favorable. However, our first-principles calculations show that both w-MnN inclusions stretched to fit the lattice constant of GaN, and relaxed ones with the equilibrium lattice constant of MnN are antiferromagnetic, and thus they are not responsible for the high temperature ferromagnetism reported for (Ga,Mn)N. Incorporation of Mn on the N sites is prohibited by the high formation energy of MnN.

CdTe buffer layers which were grown on (211)B GaAs by molecular beam epitaxy were subjected to two different etch treatments to quantify the crystal quality and dislocation density. The optical properties and thicknesses of the samples were obtained by ex situ spectroscopic ellipsometry. The surface morphologies of the CdTe epilayers were analyzed by atomic force microscopy, scanning electron microscopy, and Nomarski microscopy before and after chemical etching. We compare the triangle-and trapezoid-shaped etch pits due to the Everson and Nakagawa etch solutions, respectively. Measured etch pit density (EPD) values of triangle etch pits were found in the 8 9 10 7 cm À2 to 2 9 10 8 cm À2 range, and trapezoid-shaped etch pits were found in the 1 9 10 7 cm À2 to 7 9 10 7 cm À2 range for samples with thicknesses <2 lm.

Аннотация. Последние разработки в области физики высокоиндексных резонансных диэлектрических наноструктур предлагают альтернативные механизмы управления субволновым светом, обусловленные резонансами Ми с сильным магнитным откликом, которые могут быть использованы для создания новых оптических метаповерхностей. Здесь мы демонстрируем метаповерхности на основе наноимпринтных перовскитных пленок, оптимизированных за счет легирования органической катионной части перовскитов. Мы обнаружили, что такие метаповерхности могут демонстрировать значительное усиление как линейной, так и нелинейной фотолюминесценции (до 70 раз) в сочетании с повышенной стабильностью. Наши результаты предлагают рентабельный подход, основанный на литографии наноимпринтов и объединенный с простыми химическими реакциями для создания нового поколения функциональных метаповерхностей, которые могут проложить путь к высокоэффективным планарным оптоэлектронным метаустройствам. Ключевые слова: метаповерхность, перовскиты, фотолюминесценция, резонансы Ми, наноимпринтинг. Введение. Метаповерхности возникли как двумерные плоские структуры, состоящие из метаатомов, которые обладают особыми электромагнитными свойствами, которые не встречаются в природе . Ранние реализации таких планарных структур были основаны на благородных металлах и плазмонике. Однако высокие омические потери и нагрев плазмонных структур побудили многих исследователей искать альтернативные материалы . Совсем недавно исследование полностью диэлектрических резонансных нанофотонных структур и метаповерхностей привлекло большое внимание, поскольку они основаны на диэлектрических метаатомах с высоким показателем преломления, которые могут обеспечить множество уникальных свойств для связи света с электрическим и магнитным резонансами Ми в видимом и ближний ИК-диапазон . С другой стороны, гибридные галогенидные перовскиты недавно появились как многообещающий класс материалов для усовершенствованных оптоэлектронных устройств из-за многих преимуществ сверхдлинной диффузионной длины носителей, сильно подавленной рекомбинации носителей, низкого улавливания дефектов и примесей и высокой подвижности носителей . Что еще более важно, гибридные органо-неорганические перовскиты могут предоставить альтернативу для рентабельного производства и системной интеграции, а также являются многообещающими для светоизлучающих диодов, усилителей или лазеров . В отличие от многих активных сред на основе полупроводников, настройка спектров фотолюминесценции (ФЛ) перовскитов не требует дорогостоящих методов и требует только простых химических реакций и надлежащих методов обработки пленки, таких как разработка растворителей или горячее литье. В этой статье мы предлагаем и развиваем новую концепцию создания функциональных метаповерхностей путем создания рисунка на галогенидных перовскитах с помощью технологии наноимпринтинга, чтобы улучшить их резонансные свойства, как схематично показано на рис. 1. Мы используем экономичную и крупномасштабную литографию с наноимпринтом, последовательное тиснение методом горячего прессования для нанесения наноразмерного перовскита, пленки с покрытием, как недавно было продемонстрировано для других приложений . Что еще более важно, мы наносим оптимизированный состав тонких пленок перовскита путем легирования органической катионной части перовскитов, разработка состава тройного сплава смешанного

A method for determining the band gap value and the refractive index near the absorption edge from reflection spectra was tested for CdS x Se 1-x films prepared using the screen-printing and sintering technique. Keywords: semiconductors, CdS x Se 1-x thick films, refractive index, reflection spectra. Słowa kluczowe: półprzewodniki, warstwy CdS x Se 1-x , współczynnik załamania, widmo odbicia.

I learned pretty early in life that you don't have to learn everything to be able to do something. With inventing, you are attempting to solve a problem within your reach, not trying to resolve the world's greatest problems. -Nick Holonyak, Jr.

In this work photoacoustic conversion efficiency was analyzed in the porous silicon (PSi) and in the composite based on it, such as the "porous matrix-liquid" was analyzed. The minimum of phase on frequency dependence was observed experimentally and theoretically. This minimum is caused by summation of the different species of PA signal-thermal piston and termoelastic bending (drum effect). Experiments showed that the effective dynamic (rapid changes on temperature) coefficient of the thermal expansion of the "PSiliquid" composite exceeds the thermal expansion coefficient of the porous silicon more than in 40 times as proved by experiments conducted.

Gated transmission line model pattern measurements of the transient current–voltage characteristics of AlGaN/GaN heterostructure field-effect transistors (HFETs) and metal–oxide–semiconductor HFETs were made to develop a phenomenological model for current collapse. Our measurements show that, under pulsed gate bias, the current collapse results from increased source–gate and gate–drain resistances but not from the channel resistance under the gate. We propose a model linking this increase in series resistances (and, therefore, the current collapse) to a decrease in piezoelectric charge resulting from the gate bias-induced nonuniform strain in the AlGaN barrier layer.

The mechanism of radio-frequency current collapse in GaN–AlGaN heterojunction field-effect transistors (HFETs) was investigated using a comparative study of HFET and metal–oxide–semiconductor HFET current–voltage (I–V) and transfer characteristics under dc and short-pulsed voltage biasing. Significant current collapse occurs when the gate voltage is pulsed, whereas under drain pulsing the I–V curves are close to those in steady-state conditions. Contrary to previous reports, we conclude that the transverse electric field across the wide-band-gap barrier layer separating the gate and the channel rather than the gate or surface leakage currents or high-field effects in the gate–drain spacing is responsible for the current collapse. We find that the microwave power degradation in GaN–AlGaN HFETs can be explained by the difference between dc and pulsed I–V characteristics.

Bird Goën & Co. Klein Dalenstraat 42A 3020 Winksele (BE) (54) Improved cleaning of plasma chamber walls by adding of noble gas cleaning step (57) An improved reaction chamber and chamber cleaning process are disclosed able to remove water residues by making use of noble-gas plasma reactions. The chamber is easy to operate and the method is easily ap-plicable and may be combined with standard cleaning procedure. A noble-gas plasma (e.g. He) that emits high energy EUV photons (E>20 eV) which is able to destruct water molecules forming electronically excited oxygen atoms is used to remove the adsorbed water.