arXiv subjects

Guangying Wang

Publications and source records attributed to Guangying Wang.

7 recordsLinked to original sources

arXiv2025

Single-crystalline high-quality beta-Ga2O3 pseudo-substrate on sapphire through sputtering for epitaxial deposition

Solid-phase epitaxy (SPE) of beta-Ga2O3 thin films by radio-frequency (RF) sputtering and then crystallized through high-temperature post-deposition annealing is employed on sapphire substrates, yielding a high-quality pseudo-substrate for subsequent buffer growth via MOCVD and LPCVD. Low roughness (<0.5 nm) and sharp single-crystalline diffraction peaks corresponding to the (-201), (-402), and (-603) reflections of beta-Ga2O3 were observed in the SPE beta-Ga2O3 film and the subsequent epitaxial buffer layer. N-doped Ga2O3 film on SPE Ga2O3 film grown by LPCVD showed step-assisted growth mode with reasonable electronic behavior with 45 cm^2/V-s mobility at a bulk carrier concentration of 1.3e17 cm^-3. These results suggest that SPE Ga2O3 is a promising pathway to advance the development of beta-Ga2O3 on foreign substrates.

cond-mat.mtrl-sci↗

arXiv2025

Electrical Characterization of High-k (k>115) Crystalline SrTiO3 (STO) thin film integration with GaN with Nanomembrane Transfer Process

High-k (115), crystalline SrTiO3 (STO) thin film was transferred on GaN for potential applications in power devices (transistor and diodes) by nanomembrane transfer method and the detailed electrical properties such as leakage current, CV profiles, dielectric constant, frequency dispersion was reported from fabricated MOSCAP structures. The leakage current was negligible (under noise-level of tool) up to 6 V and 11 V for 50 nm and 200 nm STO membrane respectively A high-quality dielectric was indicated by the CV profile, which showed almost negligible frequency dispersion in the frequency range of 10 kHz to 500 kHz. The dielectric constant was 50 to 82 with the 50 nm thick STO membrane and 115 to 186 in the 200 nm thick STO membrane. Thermal annealing of the membrane in ambient conditions at 250 degrees for 2 hours led to a slight improvement in the dielectric constant (8 to 20 percent), albeit at the expense of degraded leakage current performance, as indicated by a reduction of 1 V to 3 V in the "no leakage region" of the IV curves after annealing. The possible physical mechanisms responsible for these changes were also analyzed and discussed.

cond-mat.mtrl-sci↗

arXiv2024

Demonstration of Si-doped Al-rich thin regrown Al(Ga)N films on AlN on sapphire templates with $\gt10^{15}/cm^3$ free carrier concentration using close-coupled showerhead MOCVD reactor

Thin Si-doped Al-rich (Al>0.85) regrown Al(Ga)N layers were deposited on AlN on Sapphire template using metal-organic chemical vapor deposition (MOCVD) techniques. The optimization of the deposition conditions such as temperature, V/III ratio, deposition rate, and Si concentration resulted in a high charge carrier concentration (>$10^{15}/cm^{3}$) in the Si-doped Al-rich Al(Ga)N films. A pulsed deposition condition was employed to achieve a controllable Al composition greater than 95% and to prevent unintended Ga incorporation in the AlGaN material deposited using the close-coupled showerhead reactor. Also, the effect of unintentional Si incorporation on free charge carrier concentration at the regrowth interface was observed by varying the thickness of the regrown Al(Ga)N layer. A maximum charge carrier concentration of $4.8\times 10^{16}/cm^3$ and $7.5\times 10^{15}/cm^3$ were achieved for Al0.97Ga0.03N and AlN films with thickness <300 nm compared to previously reported n-Al(Ga)N films with thickness $\ge$400 nm deposited using MOCVD technique.

physics.app-ph↗

arXiv2024

Crack-free high composition (>35%) thick (>30 nm) barrier AlGaN/AlN/GaN HEMT on sapphire with record low sheet resistance

In this article, high composition (>35%) thick (>30 nm) barrier AlGaN/AlN/GaN HEMT structure grown on a sapphire substrate with ultra-low sheet resistivity (<250 Ω/ \Box ) is reported. Optimization of growth conditions, such as reduced growth rate, low carbon incorporation, and thickness optimization of different epitaxial layers allowed to grow a crack-free high composition and thick AlGaN barrier layer HEMT structure. A significantly high two-dimensional electron gas (2DEG) density of 1.46 \times 10^{13} cm^{-2} with a room temperature mobility of 1710 cm^{2}/V.s is obtained by Hall measurement using the Van-Der-Pauw method. These state-of-the-art results show great potential for high-power Ga-polar HEMT design on the sapphire substrate.

physics.app-ph↗

arXiv2022

Tera-sample-per-second arbitrary waveform generation in the synthetic dimension

The synthetic dimension opens new horizons in quantum physics and topological photonics by enabling new dimensions for field and particle manipulations. The most appealing property of the photonic synthetic dimension is its ability to emulate high-dimensional optical behavior in a unitary physical system. Here we show that the photonic synthetic dimension can transform technical problems in photonic systems between dimensionalities, providing unexpected solutions to technical problems that are otherwise challenging. Specifically, we propose and experimentally demonstrate a photonic Galton board (PGB) in the temporal synthetic dimension, in which the temporal high-speed challenge is converted into a spatial fiber-optic length matching problem, leading to the experimental generation of tera-sample-per-second arbitrary waveforms. Limited by the speed of the measurement equipment, waveforms with sampling rates of up to 341.53 GSa/s are recorded. Our proposed PGB operating in the temporal synthetic dimension breaks the speed limit in a physical system, bringing arbitrary waveform generation into the terahertz regime. The concept of dimension conversion offers possible solutions to various physical dimension-related problems, such as super-resolution imaging, high-resolution spectroscopy, time measurement, etc.

physics.optics↗

arXiv2020

In-situ grown single crystal aluminum as a non-alloyed ohmic contact to n-ZnSe by molecular beam epitaxy (MBE)

Novel ohmic contacts to n-ZnSe are demonstrated using single crystal Al films deposited on epitaxially grown ZnSe (100) by molecular beam epitaxy (MBE). Electron Backscatter Diffraction (EBSD) confirmed the single crystalline structure of the Al films. The (110)-oriented Al layer was rotated rotated 45$^\circ$ relative to substrate to match the ZnSe (100) lattice constant. The as-grown Al-ZnSe contact exhibited nearly ideal ohmic characteristics over a large doping range of n-ZnSe without any additional treatment. The contact resistances are in a range of 10$^{-3}$ $Ω$-cm$^{2}$ for even lightly doped ZnSe ($\sim$10$^{17}$ cm$^{-3}$). Leaky Schottky behavior in lightly doped ZnSe samples suggested Al-ZnSe formed a low barrier height, Schottky limit contact. In-situ grown Al could act as a simple metal contact to n-ZnSe regardless of carrier concentration with lower resistance compared to other reported contacts in literatures. The reported novel metallization method could greatly simplify the ZnSe-based device fabrication complexity as well as lower the cost

cond-mat.mtrl-sci↗

arXiv2019

Parity-time symmetry in wavelength space with spatial singularity

Implementation of a parity-time (PT) symmetric microwave photonic system in the optical wavelength space with spatial singularity is proposed. In the proposed PT-symmetric microwave photonic system, the gain and loss modes are confined in a single spatial resonator, which is different from a conventional PT-symmetric system in which the two modes are localized in two physically separated resonators to form one-dimensional spatial potential symmetry as required by the simplest one-dimensional parity transformation. We show that PT-symmetry can be implemented between subspaces in non-spatial parameter spaces, in which the gain and loss modes can perfectly overlay spatially but are distinguishable in the designated parameter space. The resultant spatial singularity enables the possibility in implementing PT-symmetric systems with increased structural simplicity, integration density and long-term stability. To prove the concept, a PT-symmetric optoelectronic oscillator (OEO) in the optical wavelength space is implemented. The OEO has a single-loop architecture, with the gain and loss microwave modes carried by two optical wavelengths to form two mutually coupled wavelength-space resonators (WSRs). PT-symmetry is achieved by controlling the wavelength spacing and the power contrast. The operation of PT symmetry in the OEO is verified by the generation of a 10-GHz microwave signal with a low phase noise of 129.3 dBc/Hz at 10-kHz offset frequency and a high sidemode suppression ratio (SMSR) of 66.22 dB. Compared with a conventional spatial PT-symmetric system, one in the wavelength space features a much simpler configuration, better stability and greater resilience to environmental interferences.

physics.optics↗