Cathodoluminescence Spectroscopy Studies Of Aluminum Gallium Nitride And Silicon Device Structures As A Function Of Irradiation And Processing
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Cathodoluminescence Spectroscopy Studies Of Aluminum Gallium Nitride And Silicon Device Structures As A Function Of Irradiation And Processing
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Author : Brad Derek White
language : en
Publisher:
Release Date : 2006
Cathodoluminescence Spectroscopy Studies Of Aluminum Gallium Nitride And Silicon Device Structures As A Function Of Irradiation And Processing written by Brad Derek White and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Cathodoluminescence categories.
Abstract: Spatially-resolved cathodoluminescence spectroscopy (CLS) has been used to identify the presence of radiative point and extended defects in the semiconductor band gap produced by irradiation and processing conditions for Si and GaN-based devices. Changes in deep level emission in Al-SiO 2 -Si capacitor structures revealed a gradient in relative defect concentrations across the SiO 2 film after x-ray irradiation, indicating interface-specific defect creation. CLS measurements also revealed changes in the near-band edge signatures of AlGaN-GaN high-electron mobility transistor (HEMT) structures subjected to 1.8 MeV proton irradiation. These changes were indicative of alloying of AlGaN and GaN at the charge confinement interface and relaxation of piezoelectric strain in the AlGaN film. Alloying was confirmed with secondary-ion mass spectrometry, and each mechanism contributed to the measured degradation in HEMT channel transport properties. Ni-GaN Schottky barrier height decreases were also observed at lower fluences. 1.0 MeV protons were ~1.5 times more damaging than 1.8 MeV protons, which is consistent with simulations of total non-ionizing energy loss. Schottky contacts on x Al ~0.4 AlGaN were also investigated versus pre-deposition cleaning procedure. Two inductively-coupled plasma reactive-ion etching (ICP-RIE) procedures were compared with a standard HCl etch. The ICP-RIE treated samples exhibited higher uniformity than the HCl-etched surface, from electrical and CLS measurements. The presence of a spectral emission at in the HCl-etched piece correlated with the presence of a secondary Schottky barrier at ~1 eV. The emergence of a second spectral peak after ICP treatment also resulted in pinned barriers near 1 eV. A pre-metallization rapid-thermal annealing process after the ICP-RIE treatment resulted in the disappearance of both peaks, and correlated with the best diode electrical properties. The degree of Fermi level pinning from interface states, inferred from plots of extracted barrier height versus metal workfunction, was characterized for all processing conditions. Estimated interface state density was reduced by an order of magnitude for the rapid-thermal anneal process. Temperature-dependent CLS was used to assign physical origins to the defects that control the Schottky barrier properties. Nitrogen vacancies are the most probable assignment for one, or both, peaks, with the presence of screw dislocations suggested by the data.
Investigation And Characterization Of Algan Gan Device Structures And The Effects Of Material Defects And Processing On Device Performancee
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Author : Gregg Huascar Jessen
language : en
Publisher:
Release Date : 2002
Investigation And Characterization Of Algan Gan Device Structures And The Effects Of Material Defects And Processing On Device Performancee written by Gregg Huascar Jessen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Nitrides categories.
Abstract: The III-Nitride material system has proven extremely valuable for semiconductor device applications. The ability to grow high quality AlGaN/GaN that can be used for RF device applications is largely due to the commercial success of the implementation of p-type doping in GaN for optical devices. Even high quality GaN has relatively large defect densities. GaN devices are still able to achieve impressive performance, but not consistently. The variation in material quality, including deep-level defects and non-uniformities introduced by processing and growth, have deleterious effects on microwave device performance. These variations and the inability to control them reduce yield and reliability thus making AlGaN/GaN devices difficult to produce commercially. The purpose of this work is to characterize and contribute to the understanding of defects in AlGaN/GaN device systems and their effects on microwave device performance both DC and RF. The effects of device fabrication and surface processing on these defects have also been characterized. Low Energy Electron-Excited Nano-luminescence (LEEN) Spectroscopy has been used to characterize radiative defects in the AlGaN/GaN material system on a microscopic scale and compare them with electrical measurements on HEMT's and TLM structures. Salient features commonly observed in the LEEN spectra include donor-bound excitons in GaN at 3.43 eV, donor-acceptor pair transitions (DAP) at 3.30 eV, yellow luminescence (YL) centered at 2.20 eV, AlGaN donor-bound exciton emission, and associated phonon replicas. These measurements have been used to successfully correlate contact and sheet resistance with DAP, YL, and AlGaN near-band edge emission spectral features within a given wafer and between wafers. The effects of ultra-high vacuum processing with Argon sputtering and rapid thermal annealing on defects observed with LEEN spectra have been documented. Microscopic LEEN analysis has also been performed on working microwave devices and correlated to electrical measurements of frequency response, gain, and gate capacitance. Spectroscopic studies of working and failed microwave devices show that the surface and device processing changes have significant effects on device performance. These results show that it is possible to characterize and predict device performance in terms of deep level defects with non-destructive luminescence techniques on a very localized scale.
Chemical Abstracts
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Author :
language : en
Publisher:
Release Date : 2002
Chemical Abstracts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Chemistry categories.
Investigations Of The Gallium Nitride Aluminum Nitride And Indium Nitride Semiconductors Structural Optical Electronic And Interfacial Properties
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Author : Samuel Clagett Strite (III)
language : en
Publisher:
Release Date : 1993
Investigations Of The Gallium Nitride Aluminum Nitride And Indium Nitride Semiconductors Structural Optical Electronic And Interfacial Properties written by Samuel Clagett Strite (III) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with categories.
Described in this thesis is an investigation of some fundamental physical properties of both zincblende and wurtzite Group III - Nitride wide bandgap semiconductor materials. All of the thin films studied were grown by plasma-enhanced molecular beam epitaxy on either GaAs and SiC substrates. This growth method proved to be suitable for nitride expitaxial growth although compromises between the plasma power and the crystal growth rate had to be sought. The zincblende polytypes of GaN and InN were studied with the intent of evaluating their potential as a wide bandgap semiconductor system for short wavelength optical devices. The metastability of these crystals has led us to the conclusion that the zincblende nitrides are not a promising candidate for these applications due to their tendency to nucleate wurtzite domains. Bulk samples of zincblende GaN and InN and wurtzite GaN, AlN and InN were studied by x-ray photoemission spectroscopy (XPS) in an effort to determine their valence band structure. We report the various energies of the valence band density of states maxima as well as the ionicity gaps of each material. Wurtzite GaN/AlN and InN/AlN heterostructures were also investigated by XPS in order to estimate the valence band discontinuities of these heterojunctions. We measured valence band discontinuities of $Delta$E$rmsbsp{v}{GaN/AlN}$ = 0.4 $pm$ 0.4 eV and $Delta$E$rmsbsp{v}{InN/AlN}$ = 1.1 $pm$ 0.4 eV. Our results indicate that both systems have heterojunction band lineups fundamentally suitable for common optical device applications.
Deep Level Defects In Electron Irradiated Aluminum Gallium Nitride Grown By Molecular Beam Epitaxy
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Author : Michael R. Hogsed
language : en
Publisher:
Release Date : 2005
Deep Level Defects In Electron Irradiated Aluminum Gallium Nitride Grown By Molecular Beam Epitaxy written by Michael R. Hogsed and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with Epitaxy categories.
Scientific And Technical Aerospace Reports
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Author :
language : en
Publisher:
Release Date : 1982
Scientific And Technical Aerospace Reports written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1982 with Aeronautics categories.
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Aluminum Nitride Buffer Layer Growth For Group Iii Nitride Epitaxy On 111 Silicon
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Author : Andrew Philip Lange
language : en
Publisher:
Release Date : 2016
Aluminum Nitride Buffer Layer Growth For Group Iii Nitride Epitaxy On 111 Silicon written by Andrew Philip Lange and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
This dissertation examines the growth of aluminum nitride (AlN) on (111) silicon by metalorganic chemical vapor deposition. AlN is commonly used as a buffer layer for the growth of gallium nitride on silicon templates. This makes the development of growth protocols for high quality, smooth AlN films on silicon critical to improving the performance and reliability of III-nitride on silicon devices such as light emitting diodes and high power transistors. The optimal nucleation conditions for AlN on silicon have been heavily disputed. Some crystal growers expose the substrate to aluminum prior to AlN deposition, which has been shown to improve crystal quality and decrease surface roughness of both AlN buffer layers and overgrown gallium nitride. However, others adopt an ammonia-first approach, in which the substrate is nitrided prior to AlN deposition. Both can be effective depending on the growth conditions, which has resulted in considerable controversy regarding how aluminum, nitrogen, and silicon interact during these initial "predoses" and how the resulting morphology influences subsequent AlN and gallium nitride growth. The structure and morphology of aluminum predose layers deposited directly on (111) silicon at ~970 °C both with and without subsequent ammonia exposure were studied using electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Three morphological features were identified -- trenches, islands, and patches. When the predose layer was not exposed to ammonia, a roughening of the substrate was observed, similar to what occurs when gallium reacts with silicon. This gave rise to aluminum rich surface trenches, which suggests that silicon is dissolved by liquid aluminum and the resulting aluminum-silicon liquid solution evaporates. When the predose layer was exposed to ammonia, faceted patches were observed with small islands near their edges. The islands were composed of both zinc-blende and wurtzite AlN polytypes, while the patches consisted of diamond cubic silicon with dilute concentrations of aluminum. A model was proposed to explain these features in which the liquid aluminum-silicon surface layer is converted into AlN and silicon upon nitridation. Low temperature and high temperature AlN growth was examined after varied aluminum predoses using electron microscopy and atomic force microscopy with the aim of explaining anomalous AlN-silicon interface structures observed by others. AlN formed small, three-dimensional islands when grown directly on the substrate at ~970 °C with no predose. When the substrate was first exposed to a predose at ~970 °C, AlN nucleated on both island and patch features causing them to grow laterally and eventually coalesce. The morphologies of films grown with and without predoses were nearly identical after coalescence. This suggests that growth at this temperature is kinetically limited and does not depend on the nucleation surface. At high temperatures (~1060 °C), enhanced lateral growth on patch features formed during the predose was observed. The AlN-silicon interface was found to be predominantly amorphous when no predose was used, consistent with previous reports. The interface was structurally abrupt when aluminum was deposited prior to growth, but contained an additional phase consistent with the zinc-blende islands observed in predose layers. It was proposed that the amorphous SiN[subscript x] interfacial layer formed between nucleation sites when no predose was used as the substrate was exposed to an ammonia ambient prior to lateral growth of the nuclei. When the substrate was first exposed to a predose, aluminum rich silicon patches covered the surface. The presence of aluminum in the patches may limit the reaction between silicon and nitrogen during the early stages of growth. Dislocations in buffer layers grown both with and without aluminum predoses were studied using weak beam dark field transmission electron microscopy. A mosaic microstructure was observed which consisted of clustered dislocations along subgrain boundaries. Many of these subgrains were not bounded by dislocations on all sides, which suggests they did not form by the coalescence of misaligned islands. It was proposed they formed instead by the clustering of dislocations due to attractive and repulsive interactions. Dislocation densities were lower in films grown with a predose, which resulted in the formation of fewer subgrains. It was also found that buffers grown with a predose had a smoother surface. The surface of buffer layers grown without a predose contained small pits along the edges of surface terraces. The separation and geometry of these terraces was consistent with the subgrain structure, indicating surface step bunching may occur around subgrains where dislocation densities are high. Consistent with III-nitride growth on alternative substrates, a-type threading dislocations with line directions normal to the basal plane were found to terminate within highly defective, low temperature nucleation layers. C-type threading dislocations were found to terminate near the AlN-Si interface. It was suggested that the former originate from the climb of basal plane dislocations which form through the dissociation of Shockley partials or the coalescence of I1 type stacking faults. It was suggested that the latter nucleate from surface steps on the substrate. The observed improvement in crystal quality of buffer layers grown with a predose may be due to dislocation annihilation events, rather than the nucleation of fewer threading dislocations. This is corroborated by the presence of voids in the substrate when the buffer was grown with a predose, which indicates that point defects diffuse across the abrupt interface during growth. The presence of amorphous interfaces in films grown without an aluminum predose may inhibit the diffusion of point defects and thereby deter dislocation climb. If this mechanism is active as evidence in this dissertation suggests, an appropriate objective of any nucleation process for AlN buffer layers on silicon may be to improve the structural coherence of the interface.
Gallium Nitride Vertical Devices For High Power And High Frequency Applications
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Author : Siwei Li
language : en
Publisher:
Release Date : 2020
Gallium Nitride Vertical Devices For High Power And High Frequency Applications written by Siwei Li and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
Gallium nitride (GaN) has gained considerable interest in the areas of power electronics and radio frequency (RF) devices in recent years due to its significantly higher material figure-of-merits (FOMs) than silicon (Si). The capability of operating faster as power switches also overwhelms another wide-bandgap contender, silicon carbide (SiC), especially for applications at ~600-1200 V level. GaN devices with a lateral topology such as high electron mobility transistors (HEMTs) have been extensively studied, while the development of vertical devices on high-quality free-standing GaN substrates is opening new opportunities towards improved power handling capability in high-power applications. There are still science and technology issues associated with GaN that limit its applications in high-power scenarios. One of the fundamental properties is its avalanche behavior, which is expected to be considered as a benchmark for the material but was rarely seen in GaN devices grown on foreign substrates, including sapphire, Si and SiC. Avalanche is observed and gaining increasing attention recently with the improvement of GaN-on-GaN substrate, especially in diodes. Several issues of GaN in high-power and high-speed applications are addressed in the present work. Edge terminations play a vital role in GaN devices targeting a high voltage range, and enable avalanche by optimizing the electric filed distribution, eliminating peak electric field at device edges. An ion-compensated moat etch structure is studied on GaN vertical p-n diodes. Parameters including moat etching depth and ion implantation dose are optimized. P-n diodes with a breakdown voltage (V[subscript BR]) of 1500 V and a specific on-state resistance (R[subscript ON,sp]) of 0.7 m[omega]·cm2 is demonstrated with the optimized structure, showing a device FOM of 3.2 GW·cm−2 and avalanche behavior. With avalanche performance as a prerequisite confirmed on vertical p-n diodes on bulk GaN substrates with dislocation density ranging from 1e4 cm−2 to 1e6 cm−2, the effect of dislocation density on device behavior, especially off-state leakage current is experimentally and studied in detail. The leakage mechanism is analyzed by considering its relationship to electric field and temperature. Lower leakage could be achieved on the substrate with 1e4 cm−2 dislocation density, with variable-range-hopping (VRH) procedure dominating low electric field range and Poole-Frenkel (PF) effect dominating the higher part, while VRH and other more trap-related processes may play more roles on the substrate with 1e6 cm−2 dislocation density. Large current capability is another factor for high-power applications. A DC current up to 50 A is successfully demonstrated on large-area p-n diodes by applying backside gold-to-gold thermal compression bonding. A successful scaling-up is achieved with essential factors studied. There have been few works on the RF performance of GaN vertical devices though the lateral RF devices have been widely explored. To study RF properties of GaN vertical devices, a Silvaco TCAD simulation model is established for nitride (N)-polar GaN current aperture vertical electron transistor (CAVET) based on a fitting of N-polar lateral HEMT experimental results. DC and RF properties of an N-polar CAVET are simulated, and a maximum output power of 15 W·mm−1 is expected. To experimentally demonstrate RF characteristics of a CAVET, the 1st-generation RF CAVET is then built on gallium (Ga)-polar substrate. Based on the DC characteristics, a current gain cutoff frequency (fT) at ~13 GHz is expected.
Process Development For Aluminum Gallium Nitride Based Enhancement And Depletion Mode Hemts
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Author : William B. Lanford
language : en
Publisher:
Release Date : 2006
Process Development For Aluminum Gallium Nitride Based Enhancement And Depletion Mode Hemts written by William B. Lanford and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
Development And Application Of Electron Beam Induced Current And Cathodoluminescence Analytical Techniques For Characterization Of Gallium Nitride Based Devices
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Author :
language : en
Publisher:
Release Date : 2002
Development And Application Of Electron Beam Induced Current And Cathodoluminescence Analytical Techniques For Characterization Of Gallium Nitride Based Devices written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with categories.
The focus of this research was the design, development, and implementation of Electron Beam Induced Current (EBIC) and Cathodoluminescence (CL) techniques on both a Scanning Electron Microscope (SEM) and high-resolution versions on a Scanning Transmission Electron Microscope (STEM). The EBIC and CL techniques were used to characterize electrical and optical properties of fully processed gallium nitride (GaN)-based and indium gallium nitride (InGaN)-based light emitting diodes (LEDs). SEM-EBIC experiments in a linescan configuration were used to determine the minority carrier diffusion lengths of electrons and holes in a fully processed GaN-based LED. A theoretical model with an extended generation source and a nonzero surface recombination velocity was used to extract the minority carrier diffusion length of the p-type and n-type layers. A minority carrier diffusion length of L[subscript n]=(80 " 6) nm for electrons in the p-type GaN layer, L[subscript p]=(70 " 4) nm for holes in the n-type GaN: Si, Zn active layer, and L[subscript n]=(54 " 4) nm for electrons in the p-type Al[subscript 0.1]Ga[subscript 0.9]N layer were determined. The STEM-EBIC technique in a linescan configuration was used to determine the p-n junction location of an InGaN-based single quantum well LED with respect to the thin quantum well with nanometer precision. A novel sample preparation method using a Focused Ion Beam (FIB) technique and a custom STEM-EBIC sample holder were designed for these experiments. The relative position of the p-n junction with respect to the In[subscript x]Ga[subscript 1-x]N quantum well was found to be 19 " 3 nm from the center of the In[subscript x]Ga[subscript 1-x]N quantum well. In addition, the simultaneous acquisition of Z-contrast, EBIC, and elemental aluminum and indium linescans was demonstrated. Following successful implementation of the STEM-EBIC technique, several advancements to the technique were implemented. A novel sample preparati.