A5019580245- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- ZnO doping and properties
- Metal and Thin Film Mechanics
- Semiconductor materials and devices
- Semiconductor Quantum Structures and Devices
- Silicon Carbide Semiconductor Technologies
- Acoustic Wave Resonator Technologies
- Photocathodes and Microchannel Plates
- Digital Humanities and Scholarship
- Semiconductor materials and interfaces
- Radio Frequency Integrated Circuit Design
- Nanowire Synthesis and Applications
- Advancements in Semiconductor Devices and Circuit Design
- Coordination Chemistry and Organometallics
- Lanthanide and Transition Metal Complexes
- Advanced Power Amplifier Design
- Thermal Radiation and Cooling Technologies
- Silicon Nanostructures and Photoluminescence
- Cyclopropane Reaction Mechanisms
- Translation Studies and Practices
- Thermal properties of materials
University of Chinese Academy of Sciences
2024
Guizhou University of Finance and Economics
2024
Virginia Commonwealth University
2006-2011
Kyma Technologies (United States)
2010
Beijing University of Technology
2010
Ballistic and quasiballistic electron transport across the active InGaN layer are shown to be responsible for overflow electroluminescence efficiency droop at high current levels in light emitting diodes both experimentally by first-order calculations. An staircase injector with step-like increased In composition, an “electron cooler,” is proposed enhanced thermalization of injected hot electrons reduce mitigate droop. The experimental data show that results essentially same performance...
The authors report the growth of semipolar (112¯2) GaN films on nominally on-axis (101¯0) m-plane sapphire substrates using metal organic chemical vapor deposition. High-resolution x-ray diffraction (XRD) results indicate a preferred orientation. Moreover, epitaxial lateral overgrowth (ELO) was carried out oriented templates. When ELO stripes were aligned along [112¯0]sapphire, Ga-polar wings inclined by 32° with respect to substrate plane smooth extended nonpolar a-plane surfaces and polar...
We investigated the internal quantum efficiency (IQE) and relative external (EQE) of m-plane InGaN light emitting diodes (LEDs) grown on freestanding GaN at ∼400 nm for current densities up to 2500 A/cm2. IQE values extracted from intensity temperature dependent photoluminescence measurements were consistently higher, by some 30%, LEDs than reference c-plane having same structure, e.g., 80% versus 60% an injected steady-state carrier concentration 1.2×1018 cm−3. With increasing injection...
Hot electrons and the associated ballistic quasiballistic transport, heretofore neglected endemically, across active regions of InGaN light emitting diodes (LEDs) have been incorporated into a first order simple model which explains experimental observations electron spillover efficiency degradation at high injection levels. The is in good agreement with experiments wherein an adjustable barrier hot stopper, commonly called blocking layer (EBL), incorporated. also are cooled, eliminating...
We report the value of surface band bending for undoped, a-plane GaN layers grown on r-plane sapphire by metalorganic vapor phase epitaxy. The potential was measured directly ambient scanning Kelvin probe microscopy. upward films in [112¯0] direction found to be 1.1±0.1V. Because polarization effects are not present GaN, we attribute such presence charged states. have modeled assuming a localized level states gap surface. It should noted that observed is comparable obtained polar c-plane...
The optical properties of GaN films have been found to be sensitive SiNx and SiO2 surface passivation. main effect such passivation on photoluminescence (PL) data is an increase the PL intensity for near-band-edge emission. This attributed removal oxygen from subsequent formation a protective layer during in more pronounced samples passivated with SiO2, which demonstrate initially lower equilibrium concentration free electrons. A nearly constant band bending approximately 1.0 eV at has...
Significant improvement of structural and optical qualities GaN thin films on sapphire substrates was achieved by metal organic chemical vapor deposition with in situ SiNx nanonetwork. Transmission electron microscope (TEM) studies revealed that screw- edge-type dislocations were reduced to 4.4×107 1.7×107cm−2, respectively, for a ∼5.5-μm-thick layer. Furthermore, room temperature carrier lifetimes 2.22 2.49ns measured time-resolved photoluminescence (TRPL) samples containing single double...
The authors report a two-stage epitaxial lateral overgrowth (ELO) method to get uniformly coalesced (112¯0) a-plane GaN using metal organic chemical vapor deposition by employing relatively lower growth temperature in the first stage followed conditions leading enhanced second. Using ELO average Ga-polar N-polar wing rate ratio has been reduced from 4–6 1.5–2, which consequently height difference between two approaching wings at coalescence front that resulted tilt (0.44° for Ga and 0.37° N...
InGaN possesses higher electron mobility and velocity than GaN, therefore is expected to lead relatively better performances for heterostructure field effect transistors (HFETs). However, the reported mobilities AlGaN∕InGaN HFETs are lower GaN channel HFETs. To address this issue, we studied of different barriers on Hall grown by metal organic chemical vapor deposition. Unlike conventional AlGaN barrier, AlInN barrier can be at same temperature as layer, alleviating some technological...
The internal quantum efficiency (IQE) and relative external (EQE) in InGaN light-emitting diodes (LEDs) emitting at 400 nm with without electron blocking layers (EBLs) on c-plane GaN m-plane were investigated order to shed some light any effect of polarization charge induced field killer carrier spillover. Without an EBL the EQE values suffered considerably (by 80%) for both orientations, which is clearly attributable Substantial spillover polarities, therefore, suggests that not major...
We report on high electric field stress measurements at room temperature InAlN/AlN/GaN heterostructure effect transistor structures. The degradation rate as a function of the average electron density in GaN channel (as determined by gated Hall bar for particular gate biases used), has minimum densities around 1×1013 cm−2, and tends to follow hot phonon lifetime dependence density. observations are consistent with buildup longitudinal optical phonons their ultrafast decay about same channel....
The concept of nonpolar (11¯00) m-plane GaN on Si substrates has been demonstrated by initiating growth the vertical (1¯1¯1) sidewalls patterned Si(112) using metalorganic chemical vapor deposition. were wet-etched to expose {111} planes stripe-patterned SiNx masks oriented along [1¯10] direction. Only Si(1¯1¯1) allowed participate in masking other Si{111} SiO2, which led films. Growth normal surface was advance laterally and also vertically toward full coalescence. InGaN double...
We report on electron velocities deduced from current gain cutoff frequency measurements GaN heterostructure field effect transistors (HFETs) with InAlN barriers Fe-doped semi-insulating bulk substrates. The intrinsic transit time is a strong function of the applied gate bias, and minimum occurs for biases corresponding to two-dimensional gas densities near 9.3×1012 cm−2. This value correlates independently observed density giving longitudinal optical phonon lifetime. expect velocity, which...
Decay of nonequilibrium longitudinal optical (LO) phonons is investigated at room temperature in two-dimensional electron gas channels confined nearly lattice-matched InAlN/AlN/GaN structures. A nonmonotonous dependence the LO-phonon lifetime on supplied electric power reported for first time and explained terms plasmon–LO-phonon resonance tuned by applied bias a fixed sheet density (8×1012 cm−2). The shortest 30±15 fs found 20±10 nW/electron.
Heterojunction light-emitting diodes (LEDs) based on the InGaN/GaN system have improved considerably but still suffer from efficiency degradation at high injection levels which unless overcome would aggravate LED lighting. Although Auger recombination has been proposed as genesis of degradation, it appears that premise electron overflow and non-uniform distribution carriers in active region being immediate impediment is gaining popularity. The lack temperature sensitivity sizeable impact...
We report on epitaxial lateral overgrowth (ELO) of (112¯0) a-plane GaN by metalorganic chemical vapor deposition. Different growth rates Ga- and N-polar wings together with wing tilt create a major obstacle for achieving smooth, fully coalesced surface in ELO GaN. To address this issue two-step method was employed to provide large aspect ratio height width the first step followed enhanced second controlling temperature. By method, average rate has been reduced from 4–6 1.5–2, which...
We investigated internal quantum efficiency (IQE) of polar (0001) InGaN on c-sapphire, and (11¯00) nonpolar m-plane both GaN specially patterned Si. The IQE values were extracted from the resonant photoluminescence intensity versus excitation power. Data indicate that at comparable generated carrier concentrations Si is approximately a factor 2 higher than highly optimized c-plane layer. At highest laser employed (∼1.2×1018 cm−3), double heterostructure 65%. believe would remain inherently...
Abstract Grown lattice matched to GaN, InAlN‐based heterojunction field effect transistors (HFETs) are promising due the relatively large band discontinuity at interface and lack of misfit strain. Despite recent progress in growth, there still exists some questions as true matching condition InAlN GaN discrepancies value parameters InN binary, well literature bowing parameters. In order address this, we used gate lag a supplementary measurement verify underlying strain‐free layers would not...
Abstract The effect of hot electrons on electroluminescence m ‐plane double heterostructure light emitting diodes (with a single 6 nm active layer In 0.20 Ga 0.80 N) is investigated. Diodes with an electron blocking (Al 0.15 0.85 demonstrate from 3 to 5 times higher efficiency than those without layer. lower in devices the ex‐ plained terms overflow caused by ballistic and quasi‐ballistic transport injected across InGaN region. same mechanism explains decrease, observed at high current...
Abstract We report on the electrical and optical properties of InGaN based light emitting diodes (LEDs) utilizing Ga doped ZnO (GZO) grown by molecular beam epitaxy (MBE) as a highly transparent contact p‐electrode (GZO‐LEDs). For comparison, LEDs with semi‐transparent thin Ni/Au (5/5 nm) current spreading layers were also fabricated same wafer (Ni/Au‐LEDs). Unpackaged GZO‐LEDs 200 µm diameter showed negligible output degradation for up to 30 min under CW 100 mA (corresponding 318 A/cm 2...