Browsing by Author "Chiu, Hsien-Chin"

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Analysis of the back-barrier effect in AlGaN/GaN high electron mobility transistor on free-standing GaN substrates
(2020-01-25)
Liu, Xinke
;
Wang, Hao-Yu
;
Chiu, Hsien-Chin
;
Chen, Yuxuan
;
Li, Dabing
The effect of AlGaN back-barrier on AlGaN/GaN high electron mobility transistors (HEMTs) using freestanding GaN wafer has been investigated in this work. With the introducing back-barrier structure, the leakage path underneath the buffer (native nitrogen-vacancies and GaOx compounds of the HVPE-grown free-standing GaN surface) layer can be suppressed by lift-up the conduction band. As compared with AlGaN/GaN HEMTs on SiC wafer, AlGaN/GaN HEMTs on free-standing GaN wafer show enhanced drain current ( 700 mA/mm), improved transconductance (143 mS/mm), less current collapse (12%), higher current gain cut-off frequency (13 GHz), and maximum stable gain cut-off frequency (24 GHz), which is attributed to the higher epi quality layer on free-standing GaN wafer. (C) 2019 Elsevier B.V. All rights reserved.
Effect of rapid thermal annealing on Mg(x)Zn(1-x)O films prepared by radio-frequency magnetron sputtering
(2010-07-01)
Hsueh, Kuang-Po
;
Tun, Chun-Ju
;
Chiu, Hsien-Chin
;
Huang, Yu-Ping
;
Chi, Gou-Chung
This study investigates the effects of thermal annealing on the MgxZn1-xO films. MgxZn1-xO films were deposited by a radio-frequency magnetron sputtering system using a 6 in. ZnO/MgO (80/20wt%) target. The Hall results, x-ray diffraction (XRD), transmittance, and x-ray photoelectron spectroscopy (XPS) were measured. The XRD results indicate that the appearance of only (111) peaks in the as-grown MgxZn1-xO film is a sign of the cubic single phase, whereas the appearance of ZnO (002) peaks in MgxZn1-xO films annealed at 700 and 800 C confirms the formation of a wurtzite single-phase crystal. The existence of a weak (002) -wurtzite peak besides the (111)-cubic peak indicates the coexistence of two phases. The absorption spectra of MgxZn1-xO annealed at 700 and 800 C show two stages at wavelengths of 357 and 261 nm. The XPS spectra of MgxZn1-xO films were also demonstrated. The results of this study show that the ZnO films were separated from MgxZn1-xO films after higher thermal annealing. c 2010 American Vacuum Society. [DOI: 10.1116/1.3442476]
Effect of rapid thermal annealing on MgxZn1-xO films prepared by radio-frequency magnetron sputtering
(2010-07-01)
Hsueh, Kuang-Po
;
Tun, Chun-Ju
;
Chiu, Hsien-Chin
;
Huang, Yu-Ping
;
Chi, Gou-Chung
This study investigates the effects of thermal annealing on the MgxZn1-xO films. MgxZn1-xO films were deposited by a radio-frequency magnetron sputtering system using a 6 in. ZnO/MgO (80/20wt%) target. The Hall results, x-ray diffraction (XRD), transmittance, and x-ray photoelectron spectroscopy (XPS) were measured. The XRD results indicate that the appearance of only (111) peaks in the as-grown MgxZn1-xO film is a sign of the cubic single phase, whereas the appearance of ZnO (002) peaks in MgxZn1-xO films annealed at 700 and 800 C confirms the formation of a wurtzite single-phase crystal. The existence of a weak (002) -wurtzite peak besides the (111)-cubic peak indicates the coexistence of two phases. The absorption spectra of MgxZn1-xO annealed at 700 and 800 C show two stages at wavelengths of 357 and 261 nm. The XPS spectra of MgxZn1-xO films were also demonstrated. The results of this study show that the ZnO films were separated from MgxZn1-xO films after higher thermal annealing. c 2010 American Vacuum Society. [DOI: 10.1116/1.3442476]
V-Band Push-Push VCO using Slow-Wave CPW Resonators for Low Phase Noise Reduction
(2013-10-01)
Ke, Po-Yu
;
Chiu, Hsien-Chin
;
Huang, Fan-Hsiu
;
Kao, Hsuan-Ling
;
Chien, Feng-Tsun
This article presents a design for two fully integrated millimeter-wave V-band push-push voltage-controlled oscillators (VCOs) implemented in a 150-nm pHEMT process is presented. Both use slow-wave coplanar waveguide (CPW) structure transmission line resonators, instead of a lumped LC tank, to provide an extended output frequency range and relatively low phase noise (PN). A LC tank with and without slow-wave features is used in the two VCO circuits. The measured results for manufactured chips are compared. The VCO with the slow-wave feature demonstrates a lower PN of -104.5 dBc/Hz at a 1-MHz offset frequency. A comparison of the designs with and without a slow-wave VCO shows that the VCO design with slow wave demonstrates lower average PN of approximately 8 dBc at an offset frequency of 1 MHz. Varactor adjustment of the oscillation frequencies for the two VCOs gives 53.2 to 57.1 GHz for the VCO without slow wave and 53.8 to 55.4 GHz for the VCO with slow wave. The two VCOs are developed for use in licensed V-band transceiver systems. (C) 2013 Wiley Periodicals, Inc.
Vertical GaN-on-GaN PIN diodes fabricated on free-standing GaN wafer using an ammonothermal method
(2019-10-05)
Chen, Sung-Wen Huang
;
Wang, Hao-Yu
;
Hu, Cong
;
Chen, Yong
;
Wang, Hao
We report vertical GaN-on-GaN PIN diodes with a record high figure-of-merit (V-BR(2)/R-on) of 29.7 GW/cm(2) on free-standing GaN wafer using a complementary metal-oxide-semiconductor (CMOS) compatible contact materials. Due to the low substrate resistivity, low contact resistance, and high quality of GaN drift layer, a low on-state resistance R(on )of 0.31 m Omega cm(2) is obtained. With integrating of the metal filed plate structure in the vertical device, the peak electrical field along the GaN mesa edge can be significantly reduced, thus leading to a high breakdown voltage V-BR of 3.04 kV. The vertical GaN-on-GaN PIN diodes in this work show turn-on voltage V-on of similar to 3.4 V, on/off current ratio of similar to 1.3 x 10(7), and ideal factor n of similar to 2.2. According to the reverse switching measurement, the reverse recovery time T-rr. (reverse recovery charge Q(rr)) is 22.8 ns (4.8 nC) and 24.0 ns (5.4 nC), respectively, under a testing temperature of 300 K and 500 K. (C) 2019 Elsevier B.V. All rights reserved.