Browsing by Author "Chen, Lin"

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AlGaN/GaN high electron mobility transistors with a low sub-threshold swing on free-standing GaN wafer
(2017-09-01)
Liu, Xinke
;
Gu, Hong
;
Li, Kuilong
;
Guo, Lunchun
;
Zhu, Deliang
This paper reported AlGaN/GaN high electron mobility transistors (HEMTs) with low sub-threshold swing SS on free-standing GaN wafer. High quality AlGaN/GaN epi-layer has been grown by metal-organic chemical vapor deposition (MOCVD) on free-standing GaN, small full-width hall maximum (FWHM) of 42.9 arcsec for (0002) GaN XRD peaks and ultralow dislocation density (similar to 10(4)-10(5) cm(-2)) were obtained. Due to these extremely high quality material properties, the fabricated AlGaN/GaN HEMTs achieve a low SS (similar to 60 mV/decade), low hysteresis of 54 mV, and high peak electron mobility mu(eff) of similar to 1456 cm(2)V(-1)s(-1). Systematic study of materials properties and device characteristics exhibits that GaN-on-GaN AlGaN/GaNHEMTsare promising candidate for next generation high power device applications. (C) 2017 Author(s).
Design and Feasibility Analysis of Microscale Bumped Channel With Supersonic Flow for Electronics Cooling
(2016-12)
Takahashi, Yuya
;
Chen, Lin
;
Okajima, Junnosuke
;
Iga, Yuka
;
Komiya, Atsuki
In this paper, microchannel heat sink cooling device utilizing supersonic gas flow with isentropic expansion has been designed and analyzed. The objective is to study the feasibility of the supersonic microchannel with bumped section design for electronics cooling. Numerical simulations on the designed microchannel flows and heat transfer analysis have been conducted (in conjunction with a supersonic air flow inside a heated fin array) and compared with experimental results in this paper. The performance of the designed microchannel is also compared with traditional Laval nozzles for the feasibility analysis. Under 350 and 330 K inlet temperature conditions, the calculated Nu number is found higher than pure through channel flows. The supersonic expanding flow is successfully generated with lower heat transfer temperatures and a simpler geometric shape. The design of 100-300 mu m is found to have highest heat transfer for integrated microchannel width selection. For electronics cooling tests, the newly designed supersonic channel is found sufficient for a cooling capacity around 1.4 MW/m(2). In addition, the supersonic flow and heat transfer characteristics are also discussed into detail in this paper. [2016-0037]
GaN Schottky Barrier Diodes on Free-Standing GaN Wafer
(2017-01-01)
Liu, Xinke
;
Gu, Hong
;
Li, Kuilong
;
Wang, Jianfeng
;
Wang, Lei
In this paper, vertical GaN Schottky barrier diodes (SBDs) have been demonstrated on the freestanding (FS) GaN wafer. Room temperature photoluminescence shows no emission of yellow luminescence, due to the eliminating the point defects (O-N, V-Ga). The average full width half maximum (FWHM) value of.-scans for (0001) and (10-12) planes is 53 and 103 arcsec, respectively, as measured by high resolution X-ray diffraction; the average dislocation density at the top surface measured by cathodoluminescence is similar to 7.7 x 10(5) cm(-2). The vertical GaN SBDs fabricated on this FS-GaN wafer achieve a breakdown voltage of 1200 V, an on-state resistance R-on of 7 m Omega.cm(2), and a current on/off ratio I-on/I-off of similar to 2.3 x 10(10), which leads to a power device figure-of-merit V-BR(2)/R-on of 2.1 x 10(8) V-2 Omega(-1) cm(-2). TCAD simulation was employed to study the device breakdown mechanism, and shows the breakdown mechanism is due to the impact ionization at the edge of the Schottky gate. (c) 2017 The Electrochemical Society. All rights reserved.
Nearly lattice-matched molybdenum disulfide/gallium nitride heterostructure enabling high-performance phototransistors
(2019-03-01)
Liu, Xinke
;
Chen, Yuxuan
;
Li, Dabing
;
Wang, Sheng-Wen
;
Ting, Chao-Cheng
Molybdenum disulfide (MoS2)-based phototransistors are attractive for optical electronics in a large-scale size, such as transparent touch screens. However, most of the work done over the past decade has been on an opaque SiO2/Si wafer with a small size (micrometer to millimeter). In this work, a large-scale multilayer MoS2-based phototransistor has been fabricated on a transparent freestanding gallium nitride (GaN) wafer using a scalable chemical vapor deposition method. Due to the near lattice match and small thermal expansion mismatch between GaN and MoS2, the as-grown multilayer MoS2-on-GaN film shows high material quality in terms of low full width at half-maximum (similar to 5.16 cm(-1)) for the E-2g(1) Raman mode and a high absorption coefficient (similar to 10(6) cm(-1)) in the wavelength range of 405-638 nm. Under a wavelength of 405 nm at an incident power of 2 mWand applied voltage of 9 V, the fabricated MoS2-on-GaN phototransistor achieved a maximum responsivity of 17.2 A/W, a photocurrent gain of 53.6, and an external quantum efficiency of 5289%, with specific detectivity (similar to 10(10)-10(12) Jones) and low noise equivalent power (10(-12)-10(-14) W/Hz(1/2)) in the visible range of 405-638 nm. A typical response time of 0.1-4 s in the ambient air has also been recorded for the demonstrated MoS2-on-GaN phototransistor. Our work paves a technologic stepping stone for MoS2-based phototransistors for multifunctional transparent and touch-based optoelectronics in the future. (C) 2019 Chinese Laser Press