Publications by authors named "Houqiang Fu"
Epitaxial Growth of GaO: A Review.
Imteaz Rahaman Hunter D Ellis Cheng Chang Dinusha Herath Mudiyanselage Mingfei Xu Houqiang Fu Kai Fu
Materials (Basel)
August 2024
Article Synopsis
- Beta-phase gallium oxide (β-GaO) is a powerful ultrawide bandgap semiconductor, ideal for advanced power electronics and ultraviolet optoelectronics, due to its high bandgap energy and critical electric field strength.
- The review discusses recent advances in growth techniques for β-GaO, such as Molecular Beam Epitaxy and Metal-Organic Chemical Vapor Deposition, focusing on achieving high growth rates and low defect densities.
- It emphasizes the need for understanding growth processes to improve manufacturing of high-quality epitaxial structures, serving as a vital resource for engineers and researchers in the field.
Article Synopsis
- Wide bandgap semiconductors like gallium oxide (GaO) are poised to revolutionize high-power electronics, but challenges persist in fabricating effective p-n diodes.
- This study explores optimizing vertical diodes by adjusting substrate orientation, selecting different 2D materials, and using specific metal contacts, focusing on β-GaO.
- Results indicate that using a specific substrate orientation (-201), along with WS 2D layers and Ti contacts, leads to record rectification ratios and high ON-current densities, enhancing their potential for power rectifiers.
In this paper, self-powered ultraviolet (UV) photodetectors with high response performance based on GaO/p-GaN were fabricated by metal-organic chemical vapor deposition (MOCVD). The effects of different crystal phases of GaO (including , ε, ε/β, and β) grown on p-GaN films on the performance of photodetectors were systematically studied. Moreover, an GaON dielectric layer improved the responsivity of GaO/p-GaN photodetectors by 20 times.
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- This study investigates how crystalline defects, specifically threading dislocations, cause optical scattering loss in photonic waveguides made from Aluminum Nitride (AlN) in the UV-visible spectrum.
- The researchers used a volume current method along with a specific mathematical tool to understand this scattering loss, finding that it is significant in AlN that is not grown using the Metal-Organic Chemical Vapor Deposition (MOCVD) method.
- Results indicate that the loss varies with the waveguide's mode and geometry, with transverse magnetic (TM) modes showing greater loss than transverse electric (TE) modes, and larger, multimode cores being more affected by dislocations than single-mode or high-aspect-ratio waveguides.
Article Synopsis
- Researchers showcased a steep-slope field-effect transistor utilizing AlGaN/GaN MIS-HEMTs combined with SiO-based threshold switching devices, which displayed rapid resistance changes.
- The integrated device demonstrated impressive performance metrics, including a subthreshold swing of under 5 mV/decade, low leakage current, and high I/I ratio, while also exhibiting stable threshold voltage characteristics.
- This technology holds promise for enhancing various transistor platforms and could play a significant role in advancing power switching and high-frequency applications.
Article Synopsis
- The study presents the first characterizations of optical nonlinearities in beta-phase gallium oxide (β-GaO), focusing on two specific crystal orientations: (010) and (2¯01).
- Key findings include a two-photon absorption (TPA) coefficient of 1.2 cm/GW for (010) β-GaO and 0.6 cm/GW for (2¯01) β-GaO, along with Kerr nonlinear refractive indices of -2.1 × 10 cm/W and -2.9 × 10 cm/W, respectively.
- Compared to GaN, β-GaO has much smaller TPA coefficients and Kerr nonlinear values, suggesting its potential applications in ultra-low
Article Synopsis
- This study examines the loss mechanisms in III-nitride waveguides, particularly focusing on GaN in the visible light spectrum.
- It finds that free carrier loss is the main issue at low photon powers, but as power increases, two photon absorption becomes significant and eventually outweighs other losses.
- A high-performance GaN-on-sapphire waveguide was created and tested, achieving a low optical loss of about 2 dB/cm, the best reported in this spectral range, which could enhance future applications in integrated photonics and quantum optics.
Article Synopsis
- This paper presents a compact solution for detecting the direction of light using self-powered sensors integrated on a single chip.
- The light direction sensors achieve an accuracy of 1.8 degrees across a 120-degree range, with a compensation circuit improving the measurement precision to about 7 effective bits (ENOB).
- Additionally, an adaptive under voltage protection circuit is included to manage variations in power supply due to changes in temperature and manufacturing processes.
Visible light communication (VLC) holds the promise of a high-speed wireless network for indoor applications and competes with 5G radio frequency (RF) system. Although the breakthrough of gallium nitride (GaN) based micro-light-emitting-diodes (micro-LEDs) increases the -3dB modulation bandwidth exceptionally from tens of MHz to hundreds of MHz, the light collected onto a fast photo receiver drops dramatically, which determines the signal to noise ratio (SNR) of VLC. To fully implement the practical high data-rate VLC link enabled by a GaN-based micro-LED, it requires focusing optics and a tracking system.
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- The study uses the finite-difference time-domain (FDTD) method to analyze the optical properties of InGaN LEDs with metallic grating structures, focusing on aspects like the Purcell factor and light extraction efficiency.
- Light polarization significantly affects the performance metrics of the LEDs, showing strong interactions with surface plasmons generated by the metallic grating, leading to enhanced efficiencies.
- The research indicates potential for high-performance LEDs with a Purcell factor of 34 and modulation frequencies up to 5.4 GHz, offering insights for building efficient solid-state lighting and communication systems.