A5077952273- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- Semiconductor materials and devices
- ZnO doping and properties
- Nanowire Synthesis and Applications
- Metal and Thin Film Mechanics
- Silicon Carbide Semiconductor Technologies
- Semiconductor Quantum Structures and Devices
- Acoustic Wave Resonator Technologies
- 2D Materials and Applications
- Photonic and Optical Devices
- Gas Sensing Nanomaterials and Sensors
- Advanced Fiber Laser Technologies
- Thermal properties of materials
- Advancements in Semiconductor Devices and Circuit Design
- Graphene research and applications
- MXene and MAX Phase Materials
- Photocathodes and Microchannel Plates
- Optical Coatings and Gratings
- Pigment Synthesis and Properties
- Semiconductor materials and interfaces
- Catalysis and Oxidation Reactions
- Nuclear materials and radiation effects
- Catalytic Processes in Materials Science
- Transition Metal Oxide Nanomaterials
Indian Institute of Science Bangalore
2015-2023
North Carolina State University
2021-2023
Adroit Materials (United States)
2022
Shimane University
2022
Visvesvaraya National Institute of Technology
2015
We demonstrate epitaxial β-Ga2O3/GaN-based vertical metal–heterojunction-metal (MHM) broadband UV-A/UV-C photodetectors with high responsivity (3.7 A/W) at 256 and 365 nm, UV-to-visible rejection >103, a photo-to-dark current ratio of ∼100. A small (large) conduction (valence) band offset the heterojunction pulsed laser deposition (PLD)-grown β-Ga2O3 on metal organic chemical vapor (MOCVD)-grown GaN-on-silicon registry, as confirmed by X-ray diffraction (XRD) azimuthal scanning, is exploited...
We report on the highest responsivity for III-nitride Metal Semiconductor solar-blind photodetectors sapphire. Devices unintentionally doped AlGaN epilayers grown by Organic Chemical Vapor Deposition exhibited sharp absorption cut-off in range of 245–290 nm. Very high >5 A/W at 10 V bias was achieved with visible rejection exceeding three orders magnitude front illumination. Compared to values reported literature state-of-the-art photodetectors, this work presents a given and up...
We report on record high zero-bias external quantum efficiency (EQE) of 92% for back-illuminated Al0.40Ga0.60N p-i-n ultra-violet (UV) photodetectors sapphire. The zerobias responsivity measured 211 mA/W at 289 nm, which is the highest value reported solar-blind, detectors realized over any epitaxial wide band-gap semiconductor. This also first a detector, where polarization-graded Mg-doped AlGaN layer utilized as p-contact layer. devices exhibited ten-orders magnitude rectification, low...
Record low resistivities of 10 and 30 Ω cm room-temperature free hole concentrations as high 3 × 1018 cm−3 were achieved in bulk doping Mg Al0.6Ga0.4N films grown on AlN single crystalline wafer sapphire. The highly conductive exhibited a ionization energy 50 meV impurity band conduction. Both concentration (>2 1019 cm−3) compensation required to achieve conduction p-type conductivity. formation VN-related compensators was actively suppressed by chemical potential control during the...
The ultra-wide bandgap of Al-rich AlGaN is expected to support a significantly larger breakdown field compared GaN, but the reported performance thus far has been limited by use foreign substrates. In this Letter, material and electrical properties Al0.85Ga0.15N/Al0.6Ga0.4N high electron mobility transistors (HEMT) grown on 2-in. single crystal AlN substrate are investigated, it demonstrated that native substrates unlock potential for sustain large fields in such devices. We further study...
High room temperature n-type mobility, exceeding 300 cm2/Vs, was demonstrated in Si-doped AlN. Dislocations and CN−1 were identified as the main compensators for AlN grown on sapphire single crystalline substrates, respectively, limiting lower doping limit mobility. Once dislocation density reduced by growth wafers, C-related compensation could be controlling process supersaturation Fermi level during growth. While substrates supported only high ([Si] > 5 × 1018 cm−3) low mobility...
Abstract We report a kV class, low ON-resistance, vertical GaN junction barrier Schottky (JBS) diode with selective-area p-regions formed via Mg implantation followed by high-temperature, ultra-high pressure (UHP) post-implantation activation anneal. The JBS has an ideality factor of 1.03, turn-on voltage 0.75 V, and specific differential ON-resistance 0.6 mΩ·cm 2 . breakdown the is 915 corresponding to maximum electric field 3.3 MV cm −1 These results underline that high-performance can be...
Record-low p-type resistivities of 9.7 and 37 Ω cm were achieved in Al0.7Ga0.3N Al0.8Ga0.2N films, respectively, grown on single-crystal AlN substrate by metalorganic chemical vapor deposition. A two-band conduction model was introduced to explain the anomalous thermal behavior resistivity Hall coefficient. Relatively heavy Mg doping (5 × 1019 cm−3), conjunction with compensation control, enabled formation an impurity band exhibiting a shallow activation energy ∼30 meV for wide temperature...
High p-conductivity (0.7 Ω−1 cm−1) was achieved in high-Al content AlGaN via Mg doping and compositional grading. A clear transition between the valence band impurity conduction mechanisms observed. The temperature depended strongly on gradient to some degree level. model is proposed explain role of polarization field enhancing conductivity Mg-doped graded films two types. This study offers a viable path technologically useful AlGaN.
AlN Schottky barrier diodes with low ideality factor (<1.2), differential ON-resistance (<0.6 mΩ cm 2 ), high current density (>5 kA −2 and breakdown voltage (680 V) are reported. The device structure consisted of a two-layer, quasi-vertical design lightly doped drift layer highly Al 0.75 Ga 0.25 N ohmic contact grown on substrates. A combination simulation, current–voltage measurements, impedance spectroscopy analysis revealed that the AlN/AlGaN interface introduces parasitic...
Highly conductive Ge-doped AlN with conductivity of 0.3 (Ω cm)−1 and electron concentration 2 × 1018 cm−3 was realized via a non-equilibrium process comprising ion implantation annealing at moderate thermal budget. Similar to previously demonstrated shallow donor state in Si-implanted AlN, Ge also showed behavior an ionization energy ∼80 meV. 3× higher than its Si counterpart for similar doping level. Photoluminescence spectroscopy indicated that achieved primarily due lower compensation....
We report on crystalline quality-to-device performance correlation for self-powered Al0.40Ga0.60N, p–i–n ultraviolet (UV) photodetectors c-plane sapphire. The active detector stack was grown over an AlN buffer. Careful optimization of the nucleation density growth surface helped achieve a two-orders and one-order magnitude reduction in screw edge dislocation buffer layer, respectively. This resulted nine-orders reverse leakage current from 4.3 mA to 4.2 pA (at 10 V). Correspondingly,...
Near-ideal behavior in Schottky contacts to Si-doped AlN was observed as evidenced by a low ideality factor of 1.5 at room temperature. A temperature-independent barrier height 1.9 eV extracted from temperature-dependent I–V measurements. An activation energy ∼300 meV the series resistance, which corresponded ionization deep Si donor state. Both Ohmic and were stable up 650 °C, with around four orders magnitude rectification this elevated These results demonstrate potential platform for...
We report on the absence of strain relaxation mechanism in Al0.6Ga0.4N epilayers grown (0001) AlN substrates for thickness as large 3.5 μm, three-orders magnitude beyond Matthews–Blakeslee critical formation misfit dislocations (MDs). A steady-state compressive stress 3–4 GPa was observed throughout AlGaN growth leading to a lattice bow (a radius curvature 0.5 m−1) thickest sample. Despite mismatch-induced energy, exhibited smooth and crack-free surface morphology. These results point...
We report on the demonstration of UV/visible and UV/near-IR photodetectors high spectral responsivity (SR) in a non-conventional heterojunction, realized by combining multi-layered materials with wide band gap Gallium Nitride (GaN). Multi-layer MoS2 β-In2Se3 flakes were exfoliated separately epitaxial GaN-on-sapphire, followed fabrication lateral inter-digitated metal semiconductor geometry Ti/Au contacts. Devices exhibited distinct steps SR graph at 365 nm value 127 A W−1 ∼685 33 for...
Abstract We demonstrate controlled Si doping in the low range of 5 × 10 15 –2.5 16 cm −3 with mobility >1000 2 V −1 s GaN films grown by metalorganic chemical vapor deposition. The carbon-related compensation and collapse were prevented controlling electrochemical potential near growth surface via control (CPC) defect quasi-Fermi level (dQFL) point-defect management techniques. While CPC was targeted to reduce net C N concentration, dQFL used fraction atoms compensating configuration,...
Limiting buffer layer current leakage is essential for the realization of high breakdown fields in GaN-on-Si electron mobility transistors (HEMTs). In this report, we demonstrate importance controlling surface morphology AlN nucleation (NL) limiting leakage. Testing on a self-consistent series samples grown under two different NL conditions revealed presence paths within epilayers using single temperature owing to pits. The introduction higher drastically reduced pit density and led large...
We demonstrate the influence of surface terminated V-pits in tuning dark current and spectral responsivity Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> Ga xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> N-based UV-B photodetectors with metal-semiconductor-metal geometry on Si (111) substrate. show that V-pit morphological defects contribute to a large internal gain these photodetectors, thereby leading substantial...
Mg-doped, graded AlGaN films showed the formation of an impurity band and high, temperature-invariant p-conductivity even for doping levels well below Mott transition. However, compensating point defects disrupted band, resulting in Anderson transition from to valence conduction a more than tenfold reduction room-temperature conductivity. This is first demonstration Anderson-like localization films.
Si nanowire growth on sapphire substrates by the vapor-liquid-solid (VLS) method using Au catalyst particles has been studied. Sapphire was chosen as substrate to ensure that vapor phase is only source of Si. Three hitherto unreported observations are described. First, an incubation period 120–480 s, which shown be defined in classical nucleation theory, reported. This permits determination a desolvation energy from Au-Si alloys 15 kT. Two, transmission electron microscopy studies...
A predictive approach to grain size control from 10 nm 100 μm is demonstrated in chemical vapor deposited MoS2 monolayers. Such critical enabling consistent 2D electronics. Physico-chemical modeling involving adsorption–diffusion–growth–desorption equilibrium has been used correlate this variation the change supersaturation and kinetics on growth surface. The intentional addition of reaction products source chemistry shows that nucleation density (and hence final size) very sensitive initial...
A two-band transport model is proposed to explain electrical conduction in graded aluminum gallium nitride layers, where the free hole valence band favored at high temperatures and hopping impurity dominates low temperatures. The simultaneously explains significantly lowered activation energy for p-type (∼10 meV), a nearly constant sheet conductivity lower (200–330 K), anomalous reversal of Hall coefficient caused by negative sign scattering factor process. comparison between uniform samples...