A5030339641- GaN-based semiconductor devices and materials
- Semiconductor materials and devices
- Silicon Carbide Semiconductor Technologies
- Ga2O3 and related materials
- Graphene research and applications
- Molecular Junctions and Nanostructures
- ZnO doping and properties
- Electrochemical sensors and biosensors
- Advanced Photocatalysis Techniques
- Thin-Film Transistor Technologies
- Analytical Chemistry and Sensors
- Induction Heating and Inverter Technology
- Quantum and electron transport phenomena
- Electrostatic Discharge in Electronics
- Metal and Thin Film Mechanics
- Energy Harvesting in Wireless Networks
- Advancements in Semiconductor Devices and Circuit Design
- Plasma Diagnostics and Applications
- Optical measurement and interference techniques
- Surface Roughness and Optical Measurements
- Radiation Effects in Electronics
- Electronic and Structural Properties of Oxides
- Graphene and Nanomaterials Applications
- Ion-surface interactions and analysis
- Ferroelectric and Negative Capacitance Devices
Vanderbilt University
2023-2025
United States Naval Research Laboratory
2020-2023
National Postdoctoral Association
2020-2022
National Academies of Sciences, Engineering, and Medicine
2020-2021
United States Navy
2020
American Society For Engineering Education
2020
The Ohio State University
2020
Sandia National Laboratories
2020
National Health Council
2020
IBM (United States)
2018
SnSe2 field-effect transistors fabricated using mechanical exfoliation are reported. Substrate-gated devices with source-to-drain spacing of 0.5 μm have been drive current 160 μA/μm at T = 300 K. The transconductance a drain-to-source voltage Vds 2 V increases from 0.94 μS/μm K to 4.0 4.4 K, while the mobility 8.6 cm2/Vs 28 77 conductance 50 mV shows an activation energy only 5.5 meV, indicating absence significant Schottky barrier source and drain contacts.
In this work, we evaluate the quality of a commercially available GaN/AlGaN structure grown on Qromis Substrate Technology using Raman spectroscopy. Using shift E2H peak, calculated that initially GaN has lower biaxial stress than sapphire. After Cl2/Ar based reactive ion etching, surface damage was evident by an 80% increase. However, implementation wet alkaline etch treatments potassium hydroxide and tetramethyl ammonium (TMAH) relieved equal amounts. While these results indicate...
A wireless vapor sensor based on the quantum capacitance effect in graphene is demonstrated. The consists of a metal-oxide-graphene variable capacitor (varactor) coupled to an inductor, creating resonant oscillator circuit. frequency found shift proportion water concentration for relative humidity (RH) values ranging from 1% 97% with linear 5.7 kHz/%RH ± 0.3 kHz/%RH. extracted measurements agree those determined capacitance-voltage measurements, providing strong evidence that sensing arises...
Abstract The ultra-wide bandgap semiconductor gallium oxide (Ga 2 O 3 ) offers substantial promise to significantly advance power electronic devices as a result of its high breakdown electric field and maturing substrate technology. A key remaining challenge is the ability grow electronic-grade epitaxial layers at rates consistent with 20–40 μ m thick drift regions needed for 20 kV above technologies. This work reports on extensive characterization grown in novel metalorganic chemical vapor...
Understanding the interactions of ambient molecules with graphene and adjacent dielectrics is fundamental importance for a range graphene-based devices, particularly sensors, where such could influence operation device. It well-known that water can be trapped underneath its host substrate, however, electrical effect beneath dynamics how it changes different conditions has not been quantified. Here, using metal-oxide-graphene variable-capacitor (varactor) structure, we show used to...
Vertical power devices require significant attention to their edge termination designs obtain higher breakdown voltages without substantial increase in ON-state resistance. A simple structure for a GaN p-n diode is proposed, comprising full layer lightly doped p-type region underneath the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p} +\!+$ </tex-math></inline-formula> contact layer. TCAD model of...
To improve the manufacturing of vertical GaN devices for power electronics applications, effects defects in substrates need to be better understood. Many non-destructive techniques including photoluminescence, Raman spectroscopy and optical profilometry, can used detect substrate epitaxial layers. was identify points high crystal stress non-uniform conductivity a substrate, while profilometry bumps pits which could cause catastrophic device failures. The effect studied using P-i-N diodes...
Plasma etching of p-type GaN creates n-type nitrogen vacancy (VN) defects at the etched surface, which can be detrimental to device performance. In mesa isolated diodes, etch damage on sidewalls degrades ideality factor and leakage current. A treatment was developed recover both current, uses UV/O3 oxidize damaged layers followed by HF remove them. The temperature dependent I–V measurement shows that reverse transport mechanism is dominated Poole–Frenkel emission room through etch-induced VN...
The concentration-dependent density of states in graphene allows the capacitance metal–oxide–graphene structures to be tunable with carrier concentration. This feature act as a variable capacitor (varactor) that can utilized for wireless sensing applications. Surface functionalization used make sensitive particular species. In this manuscript, effect on quantum noncovalent basal plane using 1-pyrenebutanoic acid succimidyl ester and glucose oxidase is reported. It found functionalized...
We demonstrate p-type activation of GaN doped by Mg ion implantation, and in situ during metalorganic chemical vapor deposition through sequential short-duration gyrotron microwave heating cycles at temperatures 1200–1350 °C. is implanted with 1019 cm−3 ions, capped AlN, annealed under 3 MPa N2 overpressure 5 s for less than 60 total using a high-power source. Through I–V characterization, photoluminescence spectroscopy, Raman we study the evolution electrical properties, optically active...
Heterojunction field-effect transistors based on the β-(AlxGa1−x)2O3/Ga2O3 heterostructure grown by ozone-assisted molecular beam epitaxy were demonstrated for first time. Al composition ratios in 14%–23% range validated using x-ray diffraction three samples this study. Electrochemical capacitance-voltage (ECV) measurements showed presence of a charge sheet delta-doped (AlxGa1−x)2O3 barrier layer. Secondary ion mass spectroscopy and ECV also revealed an unintentional Si peak at...
The operation of multi-finger graphene quantum capacitance varactors fabricated using a planarized local bottom gate electrode, HfO2 dielectric, and large-area is described. As function the bias, devices show room-temperature tuning range 1.22–1 over voltage ±2 V. An excellent theoretical fit temperature-dependent capacitance-voltage characteristics obtained when random potential fluctuations with standard deviation 65 mV are included. results represent first step in realizing for wireless...
This article reports GaN super-heterojunction Schottky barrier diodes (SHJ-SBDs) with substantially improved performance. Metal-2DEG sidewall n-ohmic contacts were deployed to achieve low contact resistance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.75~\Omega ~ \cdot ~mm$ </tex-math></inline-formula> , avoiding the risk abnormally high caused by inaccurate etch depth control. A pGaN notch formed...
GaN devices play a major role in modern electronics, providing high-power handling, efficient high-frequency operation, and resilience harsh environments. However, electric field crowding at the edge of anode often limits its full potential, leading to single-event effects (SEEs) lower bias voltages under heavy ion radiation. Here, we report on performance homojunction vertical PiN diodes with hybrid termination design irradiation, specifically, oxygen ions, chlorine Cf-252 fission...
Abstract To improve the manufacturing process of GaN wafers, inexpensive wafer screening techniques are required to both provide feedback and prevent fabrication on low quality or defective thus reducing costs resulting from wasted processing effort. Many scale characterization techniques—including optical profilometry—produce difficult interpret results, while models using classical programming require laborious translation human-generated data interpretation methodology. Alternatively,...
This paper describes the development of vertical GaN PN diodes for high-voltage applications. A centerpiece this work is creation a foundry effort that incorporates epitaxial growth, wafer metrology, device design, processing, and characterization, reliability evaluation failure analysis. parallel aims to develop very high voltage (up 20 kV) use as devices protect electric grid against electromagnetic pulses.
GaN vertical PiN diodes with different anode thicknesses were fabricated on three native wafers the same p-layer doping concentrations, and planar hybrid edge termination. The breakdown behavior in terms of voltage electroluminescence studied as functions thickness. A repeatable avalanche highest measured thinnest 300 nm termination region. This indicates efficacy nitrogen-implanted design that comprises junction guard rings design. As thickness increases, devices exhibit lower voltages less...
GaN is a favorable martial for future efficient high voltage power switches. has not dominated the electronics market due to immature substrate, homoepitaxial growth, and processing technology. Understanding impact of substrate growth on device performance crucial boosting GaN. In this work, we studied vertical PiN diodes that were fabricated non-homogenous Hydride Vapor Phase Epitaxy (HVPE) substrates from two different vendors. We show defects which stemmed techniques manifest themselves...
In this work, a border trap model is employed to explain the observed frequency-dependent capacitance characteristics of metal-oxide-graphene (MOG) capacitors. Specifically, we have analyzed single-layer graphene capacitors with local-metal gates and HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> dielectrics, geometry which allows scaled dielectrics be analyzed, also avoids non-idealities associated dielectric nucleation on...
Abstract Foundry compatible vertical GaN PiN diodes were fabricated. The devices investigated in this work are based on 8 um drift layer thickness to achieve ∼1.2 kV of voltage blocking. Three different anode doping levels fabricated three wafers with the same p-layer thickness, and planar hybrid edge termination. moderate level 1 × 10 18 cm −3 has achieved highest breakdown 1.2 its temperature-dependent behavior proved an avalanche behavior. Furthermore, our electroluminescence displayed at...
Raman and photoluminescence mapping are used to sort GaN native substrates into two categories: those with uniform free carrier concentration large variations in concentration. Further characterization after growing 2-5 µm of homoepitaxial by metal organic chemical vapor deposition shows the substrate carry epitaxial films, as observed both techniques. This is also supported low temperature measurements, which show a broadening near band edge peak epitaxy on inhomogeneous substrates.