A5017676844- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- ZnO doping and properties
- Silicon Carbide Semiconductor Technologies
- Photonic and Optical Devices
- Nanowire Synthesis and Applications
- Metal and Thin Film Mechanics
- Advanced Fiber Laser Technologies
- Graphene research and applications
- Advanced Photocatalysis Techniques
- Diamond and Carbon-based Materials Research
- solar cell performance optimization
- Radio Frequency Integrated Circuit Design
- Advancements in Semiconductor Devices and Circuit Design
- Photocathodes and Microchannel Plates
- Boron and Carbon Nanomaterials Research
- Semiconductor materials and interfaces
- Thermal properties of materials
- Nonlinear Optical Materials Studies
- Advanced Memory and Neural Computing
- Thermal Radiation and Cooling Technologies
- Acoustic Wave Resonator Technologies
- Advanced Fiber Optic Sensors
Rice University
2021-2025
Nanjing Normal University
2024-2025
Shenzhen Bay Laboratory
2023-2024
Arizona State University
2015-2024
Max Planck Institute for the Structure and Dynamics of Matter
2023
Center for Free-Electron Laser Science
2023
University of Virginia
2023
DEVCOM Army Research Laboratory
2022-2023
United States Army Combat Capabilities Development Command
2022-2023
Oak Ridge National Laboratory
2022-2023
We report a high-power blue light-emitting diode (LED) with high external quantum efficiency and low droop on free-standing (20) GaN substrate. At forward current of 20 mA, the LED showed peak 52% an output power 30.6 mW. In higher density regions, also outstanding performance, ratios 0.7% at 35 A/cm2, 4.3% 50 8.5% 100 14.3% 200 A/cm2. The A/cm2 were 266.5 mW 45.3%, respectively.
We report indium incorporation properties on various nonpolar and semipolar free-standing GaN substrates. Electroluminescence characterization x-ray diffraction (XRD) analysis indicate that the (202¯1¯) (112¯2) planes have highest rate among studied planes. also show both composition polarization-related electric fields impact emission wavelength of quantum wells (QWs). The different magnitudes directions for each orientation result in potential profiles QWs, leading to wavelengths at a...
We demonstrate high-efficiency green and yellow-green single-quantum-well light-emitting diodes (LEDs) grown on semipolar (2021) GaN substrates by metal organic chemical vapor deposition. The output power external quantum efficiency at a driving current of 20 mA under pulsed condition with 10% duty cycle are 9.9 mW 20.4% for the LED 5.7 12.6% LED, respectively. electroluminescence linewidth narrowing, which is related to band-filling effect caused potential fluctuations, not observed.
Nonpolar and semipolar III-nitride-based blue green light-emitting diodes (LEDs) have been extensively investigated as potential replacements for current polar c-plane LEDs. High-power low-efficiency-droop LEDs demonstrated on nonpolar planes III-nitride due to the advantages of eliminated or reduced polarization-related electric field homoepitaxial growth. Semipolar (202¯1) (202¯1¯) contributed bridging "green gap" (low efficiency in spectral region) by incorporating high indium...
We demonstrate a small-area (0.1 mm2) semipolar (2021) blue (447 nm) light-emitting diode (LED) with high light output power (LOP) and external quantum efficiency (EQE) by utilizing single 12-nm-thick InGaN well. The LED had pulsed LOPs of 140, 253, 361, 460 mW, EQEs 50.1, 45.3, 43.0, 41.2%, at current densities 100, 200, 300, 400 A/cm2, respectively. device showed little shift narrow full width half maximum (FWHM). Micro-electroluminescence (µ-EL) scanning transmission electron microscope...
Vertical (-201) and (010) beta-Ga2O3 Schottky barrier diodes (SBDs) were fabricated on single-crystal substrates grown by edge-defined film-fed growth (EFG) method. High resolution X-ray diffraction (HRXRD) atomic force microscopy (AFM) confirmed good crystal quality surface morphology of the substrates. The electrical properties both devices, including current-voltage (I-V) capacitance-voltage (C-V) characteristics, comprehensively measured compared. SBDs exhibited on-resistances (Ron) 0.56...
This letter reports the implementation of double-drift-layer (DDL) design into GaN vertical Schottky barrier diodes (SBDs) grown on free-standing substrates. balances trade-off between desirable forward turn-on characteristics and high reverse breakdown capability, providing optimal overall device performances for power switching applications. With a well-controlled metalorganic chemical vapor deposition process, doping concentration top drift layer was reduced, which served to suppress peak...
Recent years have witnessed a tremendous development of vertical gallium nitride (GaN) power devices, new class device technology that could be the key enabler for next-generation high performance electronics. In this comprehensive review, we discuss recent progress made on GaN highlighting their important design principles and fabrication processes. Part I two-part review series introduces basic devices using Schottky barrier diodes (SBDs) p-n as examples. We provide in-depth analysis...
We study the optical spectral properties for green semipolar (20) and (201) light-emitting diode (LED) with same indium compositions. Compared to devices, fabricated micro-LED (∼0.005 mm2) showed negligible blue shift smaller full width at half maximum (FWHM) up extremely high current densities (10,000 A/cm2). Theoretical simulation indicates that InGaN quantum well (QW) has reduced polarization-related effects due combined of electric field cancelling Coulomb screening effect. In addition,...
The optical polarization ratio of spontaneous emission was investigated by electroluminescence measurements for semipolar (202¯1¯) InGaN/GaN light-emitting diodes, covering the blue to green spectral range. Devices fabricated on substrates exhibit ratios ranging from 0.46 at 418 nm 0.67 519 nm. These are significantly higher than those reported (202¯1) devices. valence band energy separation is extracted and consistent with increased theoretical predictions. Quantum well interdiffusion...
This letter reports the first demonstration of 1-kV-class AlN Schottky barrier diodes on sapphire substrates by metal organic chemical vapor deposition. The device structure mimics silicon-on-insulator (SOI) technology, consisting thin <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> -AlN epilayer as active region and thick resistive underlayer insulator. At room temperature,...
To mimic selective-area doping, p-GaN was regrown on an etched GaN surface substrates by metalorganic chemical vapor deposition. Vertical GaN-on-GaN p-n diodes were fabricated to investigate the effects of etch-then-regrowth process device performance. The crystal quality sample after each epitaxial step characterized X-ray diffraction, where led a very slight increase in edge dislocations. A regrowth interfacial layer clearly shown transmission electron microscopy. Strong...
This work demonstrates the construction of p-n heterojunctions between mechanically exfoliated beta-phase gallium oxide (β-Ga2O3) and p-GaN. The detailed mechanical exfoliation process was developed can be used for further device applications. atomic force microscopy study showed that β-Ga2O3 flakes had a very smooth surface with roughness 0.65 nm. Transmission electron revealed clearly defined interface heterojunction exhibited turn-on voltage 3.6 V rectification ratio ∼105. also good...
This letter demonstrates novel hydrogen-plasma based guard rings (GRs) for high voltage vertical GaN p-n diodes grown on bulk substrates by metalorganic chemical vapor deposition (MOCVD). The GR structure can significantly improve breakdown voltages (BV) and critical electric fields (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of the devices. Not having field plates or passivation, with a 9 μm drift layer 10 GRs showed...
This letter reports high performance GaN p-n junctions with regrown p-GaN by metalorganic chemical vapor deposition (MOCVD) on dry-etched surfaces. The breakdown voltage reaches 1.27 kV and the differential on-resistance is 0.8 m · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . effects of etching powers surface treatments reverse leakage characteristics have been investigated. It's found that lowering power damage very effective to...
Vertical GaN-on-GaN Schottky barrier diodes based on as-grown and regrown samples were fabricated to investigate the effects of etch-then-regrow process device performance. The surface roughness increased slightly after dry etching decreased regrowth. According X-ray diffraction results, caused a slight increase defect density due edge dislocations. parameters extracted from forward current-voltage curves, such as turn-on voltages 0.74 V 0.72 V, ideality factors 1.07 1.10, heights eV 1.05...
Vertical gallium nitride (GaN) power devices are enabling next-generation electronic and systems with higher energy efficiency, density, faster switching, smaller form factor. In Part I of this review, we have reviewed the basic design principles physics building blocks vertical GaN devices, i.e., Schottky barrier diodes p-n diodes. Key topics such as materials engineering, device avalanche breakdown, leakage mechanisms discussed. II several more advanced rectifiers discussed, including...
High-surface-area α-Al2O3 nanoparticles are used in high-strength ceramics and stable catalyst supports. The production of by phase transformation from γ-Al2O3 is hampered a high activation energy barrier, which usually requires extended high-temperature annealing (~1500 K, > 10 h) suffers aggregation. Here, we report the synthesis dehydrated (phase purity ~100%, particle size ~23 nm, surface area ~65 m2 g-1) pulsed direct current Joule heating γ-Al2O3. completed at reduced bulk temperature...
This letter reports an enhancement-mode (E-mode) GaN transistor technology which has been demonstrated to operate in a simulated Venus environment (460 °C, ~ 92 atm., containing CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /N /SO etc.) for 10 days. The robustness of the W/p-GaN-gate AlGaN/GaN high electron mobility (HEMT) was evaluated by two complementary approaches, (1) <italic...
The first 30-mW-class semipolar blue light-emitting diode (LED) on a free-standing (10) GaN substrate has been demonstrated by using microscale periodic backside structures. light extraction efficiency and corresponding output power were greatly enhanced, up to 2.8-fold (bare chip) compare with conventional devices. At driving current of 20 mA, the LED showed an 31.1 mW external quantum 54.7%. Semipolar technology is now comparable commercial c-plane technology, not only in terms internal...
This letter reports the first implementation of a hydrogen-plasma-based edge termination technique (HPET) in vertical GaN p-n power diodes grown on bulk substrates using metalorganic chemical vapor deposition. The device with 9-μm-thick drift layer exhibited high breakdown voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bd</sub> ) 1.57 kV, low ON-resistance (R xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> 0.45 mQ · cm <sup...
We investigate thermoelectric pumping in wide-bandgap GaN based light-emitting diodes (LEDs) to take advantage of high junction temperature rather than avoiding the problem temperature-induced efficiency droop through external cooling. experimentally demonstrate a thermally enhanced 450 nm LED, which nearly fourfold light output power is achieved at 615 K (compared 295 room operation), with no reduction wall-plug (i.e., electrical-optical energy conversion efficiency) bias V&lt;ℏω/q. The...