A5028030922- Semiconductor materials and devices
- Silicon Carbide Semiconductor Technologies
- Semiconductor materials and interfaces
- Ga2O3 and related materials
- ZnO doping and properties
- Electronic and Structural Properties of Oxides
- Advanced Photocatalysis Techniques
- Integrated Circuits and Semiconductor Failure Analysis
- GaN-based semiconductor devices and materials
- Metal and Thin Film Mechanics
- Electron and X-Ray Spectroscopy Techniques
- Silicon and Solar Cell Technologies
- Diamond and Carbon-based Materials Research
- Thin-Film Transistor Technologies
- Organic Electronics and Photovoltaics
- Advancements in Semiconductor Devices and Circuit Design
- Copper Interconnects and Reliability
- Advanced ceramic materials synthesis
- Advanced Sensor and Energy Harvesting Materials
- Gas Sensing Nanomaterials and Sensors
- Chalcogenide Semiconductor Thin Films
- Aluminum Alloys Composites Properties
- Magnetic and transport properties of perovskites and related materials
- Advanced Materials Characterization Techniques
- Advanced Electron Microscopy Techniques and Applications
Brigham and Women's Hospital
2025
Harvard University
2025
Carnegie Mellon University
2014-2024
North Carolina State University
1992-2021
Indian Institute of Technology Roorkee
2021
University of Warwick
2021
United States Air Force Research Laboratory
2021
Georgia Institute of Technology
2021
University of Wisconsin–Madison
2021
University of South Carolina
2021
Heteroepitaxial films of GaO were grown on c-plane sapphire (0001). The stable phase β-GaO was using the metalorganic chemical vapor deposition technique, regardless precursor flow rates, at temperatures between 500C and 850C. Metastable α- ϵ-phases when halide epitaxy (HVPE) growth 650C 850C, both separately in combination. XTEM revealed better lattice-matched α-phase growing semi-coherently substrate, followed by ϵ-GaO. epitaxial relationship determined to be [] ϵ-GaO α-GaO α-AlO. SIMS...
High carbon concentrations at distinct regions thermally-grown SiO2/6H–SiC(0001) interfaces have been detected by electron energy loss spectroscopy (EELS). The thickness of these C-rich is estimated to be 10–15 Å. oxides were grown on n-type 6H–SiC 1100 °C in a wet O2 ambient for 4 h immediately after cleaning the substrates with complete RCA process. In contrast, not from EELS analyses thermally SiO2/Si nor chemical vapor deposition deposited SiO2/SiC interfaces. Silicon-rich layers within...
The specific contact resistance of an ohmic will be discussed including ways to calculate and measure this parameter. Ohmic contacts n- p-type hexagonal SiC then detailed. Low n-type are predominately fabricated by annealing a refractory metal, thereby forming silicide with lowered Schottky barrier height at the metal–SiC interface. P-type on other hand generally use Al or alloys which upon enable diffuse into thus resulting in properties. Aluminium however suffer from many problems...
Schottky diodes based on (2¯01) β-Ga2O3 substrates and (010) homoepitaxial layers were formed using five different metals: W, Cu, Ni, Ir, Pt. Based a comparison of the effects wet chemical surface treatments Ga2O3 diodes, it was established that treatment with an organic solvent, cleaning HCl H2O2, rinsing deionized water following each step yielded best results. barrier heights calculated from current–voltage (I-V) capacitance–voltage (C-V) measurements selected metals typically in range...
This study reports UV-photoemission (UPS) measurements made on boron nitride crystals and thin films. The materials examined are commercial grade c-BN powder films of BN deposited with ion beam assisted e-beam evaporation laser ablation. film samples exhibited varying amounts sp3 (cubic) sp2 (hexagonal, amorphous) bonding as determined by FTIR measurements. UPS displayed the spectral distribution low energy photoemitted electrons total width spectra. These characteristics can be related to...
The Schottky barriers of Ti, Mo, Co, Ni, Pd, and Au on (100) β-Ga2O3 substrates were analyzed using a combination current-voltage (J-V), capacitance-voltage (C-V), current-voltage-temperature (J-V-T) measurements. Near-ideal, average ideality factors for Ni 1.05–1.15, whereas higher (∼1.3) observed Pd contacts. Barrier heights ranging from 0.60 to 1.20 eV calculated J-V measurements the metals with low factors. C-V all conducted yielded barrier 0.78 1.98 eV. J-V-T Ti Co diodes 0.81 1.35 eV,...
Nominally phase-pure γ-Ga2O3 was deposited on (100) MgAl2O4 within a narrow temperature window centered at ∼470 °C using metal-organic chemical vapor deposition. The film 440 exhibited either poor crystallization or an amorphous structure; the grown 500 contained both β-Ga2O3 and γ-Ga2O3. A nominally obtained 530 °C. Atomic-resolution scanning transmission electron microscopy (STEM) investigations of 470 revealed high density antiphase boundaries. planar defect model developed for γ-Al2O3...
We investigated arrays of Ni, Pt, or Ti Schottky diodes on n-type 4H-SiC epitaxial layers using current-voltage (I-V) measurements, electron beam induced current (EBIC), polarized light microscopy, x-ray topography, and depth-resolved cathodoluminescence spectroscopy. A significant percentage (∼7%–30% depending growth method diode size) displayed “nonideal” inhomogeneous barrier height characteristics. used a thermionic emission model based two parallel to determine the heights ideality...
Chemical and electrical measurements of Ti/(010) β-Ga2O3 Ti/(001) interfaces were conducted as a function annealing temperature using x-ray photoelectron spectroscopy (XPS), current density–voltage (J–V), capacitance–voltage (C–V) measurements. XPS revealed partial Ti oxidation at both in the as-deposited condition, with more on (001) epilayer surface than (010) substrate surface. The amount oxidized increased temperature. Schottky barrier heights for (unannealed) Au/Ti/(010) Au/Ti/(001)...
Risk alleles in lysine specific demethylase 1 (LSD1) and striatin (STRN) are independently associated with greater salt sensitive blood pressure (SSBP) increased aldosterone and/or mineralocorticoid receptor (MR) activity. We tested the hypothesis that Black, but not White, risk allele carriers both genes would have a more severe degree of SSBP than those carrying single from either gene alone. Individuals HyperPATH cohort were assessed for hormone levels after controlled low liberal sodium...
Silicon has been the semiconductor of choice for microelectronics largely because unique properties its native oxide (SiO2) and Si/SiO2 interface. For high-temperature and/or high-power applications, however, one needs a with wider energy gap higher thermal conductivity. carbide right same as Si. However, in late 1990’s it was found that SiC/SiO2 interface had high trap densities, resulting poor electron mobilities. Annealing hydrogen, which is key to quality interfaces, proved ineffective....
Thermal conductivities (k) of the individual layers a GaN-based light emitting diode (LED) were measured along [0001] using 3-omega method from 100-400 K. Base AlN, GaN, and InGaN, grown by organometallic vapor phase epitaxy on SiC, have effective k much lower than bulk values. The 100 nm thick AlN layer has = 0.93 ± 0.16 W/mK at 300 K, which is suppressed >100 times relative to AlN. Transmission electron microscope images revealed high dislocation densities (4 × 1010 cm−2) within...
From an analysis of Pd contact Schottky diodes fabricated on (100) β-Ga2O3 wafers, in combination with data extracted from published work, we show that the barrier height inhomogeneity commonly observed has a strong correlation to temperature. For doping ∼5 × 1017 cm−3, arising inhomogeneous continues increase temperature ∼440 K followed by decrease upon further temperature, which is attributed bandgap narrowing semiconductor referred as Varshni shift. At this regime, characteristics...
Phase and microstructural evolution of gallium oxide (Ga2O3) films grown on vicinal (0001) sapphire substrates was investigated using a suite analytical tools. High-resolution transmission electron microscopy scanning film at 530 °C revealed the initial pseudomorphic growth three to four monolayers α-Ga2O3, 20–60 nm transition layer that contained both β- γ-Ga2O3, top ∼700 nm-thick phase-pure κ-Ga2O3. Explanations for occurrence these phases their sequence formation are presented. Additional...
A near-ideal and homogeneous β-Ga2O3 Schottky diode with Co contact for a doping level of ∼4.2 × 1017 cm−3 in the drift layer where Boltzmann approximation is valid reported. Unlike Si or GaN, thermionic emission shown to be dominant current conduction mechanism at this level. wide depletion region appended large built-in potential observed limit field current, which otherwise evident narrower bandgap semiconductor (such as GaN) diodes having similar carrier concentration region. The results...
Phase transitions in metastable α-, κ(ε)-, and γ-Ga2O3 films to thermodynamically stable β-Ga2O3 during annealing air, N2, vacuum have been systematically investigated via situ high-temperature x-ray diffraction (HT-XRD) scanning electron microscopy (SEM). These respective polymorphs exhibited thermal stability ∼471–525 °C, ∼773–825 ∼490–575 °C before transforming into β-Ga2O3, across all tested ambient conditions. Particular crystallographic orientation relationships were observed after the...
Charge injection and transport in bottom-contact regioregular-poly(3-hexylthiophene) (rr-P3HT) based field-effect transistors (FETs), wherein the Au source drain contacts are modified by self-assembled monolayers (SAMs), is reported at different channel length scales. Ultraviolet photoelectron spectroscopy used to measure change metal work function upon treatment with four SAMs consisting of thiol-adsorbates chemical composition. Treatment FETs electron-poor (electron-rich) resulted an...
In this study, electrical properties of four metals (W, Mo, Au, Ni) as Schottky contacts on n-type (100)-oriented β-Ga2O3 substrates grown by the Czochralski method are reported. The barrier heights for each metal contact were calculated from I-V and/or C-V measurements. Two methods used to cross check (φB) and ideality factors (n) height values measurements showed excellent agreement with other increased an increase in work functions. Some anomalous behavior Au contacts, which is similar...
Ga2O3 films were deposited on (100) MgAl2O4 spinel substrates at 550, 650, 750, and 850 °C using metal-organic chemical vapor deposition investigated x-ray diffraction transmission electron microscopy. A phase-pure γ-Ga2O3-based material having an inverse structure was formed °C; a mixture of the γ-phase β-Ga2O3 detected in grown 750 °C. Only determined 650 550 β- to transition occurred from substrate/film interface during growth The stabilization outset film affected by substantial Mg Al...
High-resolution elemental profiles were obtained from SiO2(N)∕4H-SiC structures by spatially resolved electron energy-loss spectroscopy (EELS) performed in the scanning transmission microscopy mode. The results show that following annealing NO, N was exclusively incorporated within ∼1nm of interface. Mean interfacial nitrogen areal densities measured EELS ∼(1.0±0.2)×1015cm−2 carbon-face samples and (0.35±0.13)×1015cm−2 Si-face samples; these are consistent with nuclear reaction analysis...