A5034929939- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- Semiconductor materials and devices
- ZnO doping and properties
- Semiconductor Quantum Structures and Devices
- Electronic and Structural Properties of Oxides
- Radio Frequency Integrated Circuit Design
- Advanced Photocatalysis Techniques
- Advancements in Semiconductor Devices and Circuit Design
- 2D Materials and Applications
- Silicon Carbide Semiconductor Technologies
- Metal and Thin Film Mechanics
- Graphene research and applications
- MXene and MAX Phase Materials
- Photocathodes and Microchannel Plates
- Acoustic Wave Resonator Technologies
- Ferroelectric and Piezoelectric Materials
- Nanowire Synthesis and Applications
- Magnetic and transport properties of perovskites and related materials
- Semiconductor Lasers and Optical Devices
- Semiconductor materials and interfaces
- Ferroelectric and Negative Capacitance Devices
- Quantum and electron transport phenomena
- Chalcogenide Semiconductor Thin Films
- Advanced MEMS and NEMS Technologies
The Ohio State University
2016-2025
Washington State University
2022
University of California, Santa Barbara
2004-2021
Wright State University
2018-2021
United States Air Force Research Laboratory
2021
University of Utah
2017-2020
Pennsylvania State University
2020
Kyma Technologies (United States)
2020
University of South Carolina
2020
Indian Institute of Technology Bombay
2018-2019
Abstract Ultrawide‐bandgap (UWBG) semiconductors, with bandgaps significantly wider than the 3.4 eV of GaN, represent an exciting and challenging new area research in semiconductor materials, physics, devices, applications. Because many figures‐of‐merit for device performance scale nonlinearly bandgap, these semiconductors have long been known to compelling potential advantages over their narrower‐bandgap cousins high‐power RF electronics, as well deep‐UV optoelectronics, quantum...
Monolayer van der Waals (vdW) magnets provide an exciting opportunity for exploring two-dimensional (2D) magnetism scientific and technological advances, but the intrinsic ferromagnetism has only been observed at low temperatures. Here, we report observation of room temperature in manganese selenide (MnSe$_x$) films grown by molecular beam epitaxy (MBE). Magnetic structural characterization provides strong evidence that monolayer limit, originates from a vdW diselenide (MnSe$_2$) monolayer,...
We report on the fabrication and high-frequency characterization of AlGaN/GaN high-electron mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) metal-organic chemical vapor deposition (MOCVD). In devices with a gate length 160 nm, record power density 10.5 W/mm 34% added efficiency (PAE) has been measured at 40 GHz in MOCVD-grown HEMTs biased V/sub DS/=30 V. Under similar bias conditions, more than 8.6 W/mm, 32% PAE, were obtained MBE-grown sample. The dependence output power,...
Solid state UV emitters have many advantages over conventional sources. The (Al,In,Ga)N material system is best suited to produce LEDs and laser diodes from 400 nm down 210 nm—due its large tuneable direct band gap, n- p-doping capability up the largest bandgap AlN a growth fabrication technology compatible with current visible InGaN-based LED production. However AlGaN based UV-emitters still suffer numerous challenges compared their counterparts that become most obvious by consideration of...
Gallium Oxide has undergone rapid technological maturation over the last decade, pushing it to forefront of ultra-wide band gap semiconductor technologies. Maximizing potential for a new system requires concerted effort by community address technical barriers which limit performance. Due favorable intrinsic material properties gallium oxide, namely, critical field strength, widely tunable conductivity, mobility, and melt-based bulk growth, major targeted application space is power...
In this work, we demonstrate a high mobility two-dimensional electron gas (2DEG) formed at the β-(AlxGa1-x)2O3/Ga2O3 interface through modulation doping. Shubnikov-de Haas (SdH) oscillations were observed in modulation-doped structure, indicating high-quality channel heterojunction interface. The formation of 2DEG was further confirmed by weak temperature dependence carrier density, and peak low found to be 2790 cm2/Vs, which is significantly higher than that achieved bulk-doped Beta-phase...
We report on the first demonstration of p-type doping in large area few-layer films (0001)-oriented chemical vapor deposited MoS2. Niobium was found to act as an efficient acceptor up relatively high density MoS2 films. For a hole 3.1 × 1020 cm−3, Hall mobility 8.5 cm2 V−1 s−1 determined, which matches well with theoretically expected values. X-ray diffraction scans and Raman characterization indicated that film had good out-of-plane crystalline quality. Absorption measurements showed doped...
Modulation-doped heterostructures are a key enabler for realizing high mobility and better scaling properties performance transistors. We report the realization of modulation-doped two-dimensional electron gas (2DEG) at beta(Al0.2Ga0.8)2O3/ Ga2O3 heterojunction using silicon delta doping. The formation 2DEG was confirmed capacitance voltage measurements. A channel used to realize field-effect transistor. demonstration modulation doping in beta-(Al0.2Ga0.8)2O3/ material system could enable...
Heterostructures and superlattices consisting of a prototype Mott insulator, GdTiO3, the band insulator SrTiO3 are grown by molecular beam epitaxy show intrinsic electronic reconstruction, approximately ½ electron per surface unit cell at each GdTiO3/SrTiO3 interface. The sheet carrier densities in all structures containing more than one independent layer thicknesses growth sequences, indicating that mobile carriers high concentration, two-dimensional gas bound to These closely meet...
In this report, we demonstrate high spectral responsivity (SR) in MBE grown epitaxial \b{eta}-Ga2O3-based solar blind MSM photodetectors (PD). (-2 0 1)-oriented \b{eta}-Ga2O3 thin film was by plasma-assisted on c-plane sapphire substrates. devices fabricated with Ni/Au contacts an interdigitated geometry were found to exhibit peak SR > 1.5 A/W at 236-240 nm a bias of 4 V UV visible rejection ratio 105. The exhibited very low dark current < 10 nA 20 and showed no persistent photoconductivity...
This paper reviews the progress of N-polar () GaN high frequency electronics that aims at addressing device scaling challenges faced by electron mobility transistors (HEMTs) for radio-frequency and mixed-signal applications. Device quality (Al, In, Ga)N materials heterostructures are developed using molecular beam epitaxy metalorganic chemical vapor deposition. The principles polarization engineering designing HEMT structures will be outlined. performance, behavior microwave power devices as...
We describe the development of N-polar GaN-based high electron mobility transistors grown by N2 plasma-assisted molecular beam epitaxy on C-face SiC substrates. High AlGaN∕GaN modulation-doped two-dimensional gas channels were grown, and with excellent dc small-signal performance fabricated these wafers. Large-signal dispersion was observed, trap states responsible for this identified, layer designs to remove dispersive effects traps demonstrated. Finally, an AlGaN-cap used reduce gate...
The decrease of transconductance g/sub m/ and current gain cutoff frequency f/sub T/ at high drain levels in AlGaN/GaN high-electron mobility transistors (HEMTs) severely limits the linearity power performance these devices frequencies. In this paper, increase differential source access resistance r/sub s/, with is shown to play an important role fall T/. s/ occurs due quasi-saturation electron velocity region channel electric fields higher than 10 kV/cm. This has been confirmed by both...
Layered metal dichalcogenide materials are a family of semiconductors with wide range energy band gaps and properties, potential to open up new areas physics technology applications. However, obtaining high crystal quality thin films over large area remains challenge. Here we show that chemical vapor deposition (CVD) can be used achieve electronic grade single Molybdenum Disulfide (MoS2) the highest mobility reported in CVD grown so far. Growth temperature choice substrate were found...
We report on our investigation of the electrical properties metal/Al2O3/GaN metal-insulator-semiconductor capacitors. determined conduction band offset and interface charge density alumina/GaN by analyzing capacitance-voltage characteristics atomic layer deposited Al2O3 films GaN substrates. The at Al2O3/GaN was calculated to be 2.13 eV, in agreement with theoretical predications. A non-zero field 0.93 MV/cm oxide under flat-band conditions inferred, which we attribute a fixed net positive...
In this letter, we experimentally demonstrate direct correlation between efficiency droop and carrier overflow in InGaN/GaN green light emitting diodes (LEDs). Further, flat external quantum curve up to 400 A/cm2 a plasma assisted molecular beam epitaxy grown N-polar double well LED without electron blocking layers. This is achieved by exploring the superior properties of reverse polarization field N-face polarity, such as effective injection higher potential barriers against mechanism. The...
In this work, we demonstrate modulation-doped β-(AlxGa1-x)2O3/Ga2O3 double heterostructure field effect transistors. The maximum sheet carrier density for a two-dimensional electron gas (2DEG) in is limited by the conduction band offset and parasitic channel formation barrier layer. We to realize β-(AlxGa1-x)2O3/Ga2O3/(AlxGa1-x)2O3 quantum well, where electrons can be transferred from below above β-Ga2O3 well. confined 2DEG charge of 3.85 × 1012 cm−2 was estimated low-temperature Hall...
We report on the design and demonstration of polarization-engineered GaN/InGaN/GaN tunnel junction diodes with high current density low tunneling turn-on voltage. Wentzel–Kramers–Brillouin calculations were used to model junctions narrow band gap InGaN-based barrier layers. N-polar p-GaN/In0.33Ga0.67N/n-GaN heterostructure grown using molecular beam epitaxy. Efficient interband was achieved close zero bias a 118 A/cm2 at reverse 1 V, reaching maximum up 9.2 kA/cm2. These results represent...
GaN, a wide bandgap semiconductor successfully implemented in optical and high-speed electronic devices, has gained momentum recent years for power electronics applications. Along with rapid progress material device processing technologies, high-voltage transistors over 600 V have been reported by number of teams worldwide. These advances make GaN highly attractive the growing market electrified vehicles, which currently employ bipolar silicon devices 600–1200 class traction inverter....
We used depth-resolved cathodoluminescence spectroscopy and surface photovoltage to measure the effects of near-surface plasma processing neutron irradiation on native point defects in β-Ga2O3. The sensitivity depth resolution these optical techniques enabled us identify spectral changes associated with removing or creating defects, leading identification one oxygen vacancy-related two gallium energy levels β-Ga2O3 bandgap. combined detection Ga2O3 suggests an avenue for identifying physical...
As an ultra-wide bandgap semiconductor, β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> has attracted great attention for high-power, high-voltage, and optoelectronic applications. However, until now, high-frequency performance of gallium oxide devices been limited to relatively low current gain cutoff frequencies below 5 GHz. Here, we show that highly localized delta-doping...
We report silicon delta doping in Gallium Oxide (\b{eta}-Ga2O3) grown by plasma assisted molecular beam epitaxy using a shutter pulsing technique. describe growth procedures that can be used to realize high Si incorporation an oxidizing oxygen environment. Delta was thin (12 nm) low-resistance layers with sheet resistance of 320 Ohm/square (mobility 83 cm^2/Vs, integrated charge 2.4x10^14 cm^-2). A single delta-doped carriers employed as channel field effect transistor current ID,MAX =292...
We report (010)-oriented β-Ga2O3 bevel-field-plated mesa Schottky barrier diodes grown by low-pressure chemical vapor deposition (LPCVD) using a solid Ga precursor and O2 SiCl4 sources. with good ideality low reverse leakage were realized on the epitaxial material. Edge termination beveled field plates yielded breakdown voltage of −190 V, maximum vertical electric fields 4.2 MV/cm in center 5.9 at edge estimated, extrinsic RON 3.9 mΩ·cm2 extracted intrinsic 0.023 mΩ·cm2. The reported results...
The polar nature of the wurtzite crystalline structure GaN and ZnO results in existence a spontaneous electric polarization within these materials their associated alloys (Ga,Al,In)N (Zn,Mg,Cd)O. polarity has also important consequences on stability different crystallographic surfaces, this becomes especially when considering epitaxial growth. Furthermore, internal fields may adversely affect properties optoelectronic devices but is used as potential advantage for advanced electronic...