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Yu Huei Wu

Bio: Yu Huei Wu is an academic researcher from National Cheng Kung University. The author has contributed to research in topics: Heterojunction & Electron mobility. The author has an hindex of 4, co-authored 7 publications receiving 54 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, an improved In 0.5Ga0.5P/GaAs double heterostructure-emitter bipolar transistor (DHEBT) has been fabricated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD).
Abstract: An improved In0.5Ga0.5P/GaAs double heterostructure-emitter bipolar transistor (DHEBT) has been fabricated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The 100 A undoped GaAs spacers grown on both sides of the base are used to improve the recombination of p-n interface and to increase the common-emitter current gain. The emitter edge-thinning technique is used to reduce the surface recombination current and improve the current gain. A current gain of 180 with an offset voltage as low as 60 mV are achieved. Meanwhile, Gummel plot is shown to understand the composition of collector and base currents.

24 citations

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TL;DR: In this article, a Mg-doped insulating GaN layer is inserted to suppress the leakage current, improve the breakdown voltages, and yield excellent pinch-off characteristics.
Abstract: Al 0. 32 Ga 0. 68 N/GaN heterostructure field-effect transistors (HFETs) grown by low-pressure metallorganic chemical vapor deposition are successfully fabricated. A Mg-doped insulating GaN layer is inserted to suppress the leakage current, improve the breakdown voltages, and yield excellent pinch-off characteristics. Moreover, HFETs with different channel thicknesses of 1200, 1500, and 1800 A are investigated. Experimental results show that an HFET with a 1800 A thick channel layer has the highest electron mobility, electron concentration, drain current, and extrinsic transconductance.

13 citations

Journal ArticleDOI
TL;DR: In this article, a two-terminal real-space transfer diode (RSTD) using a InAlAs/InGaAs heterojunction grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) is presented.
Abstract: We report a two-terminal real-space transfer diode (RSTD) using a InAlAs/InGaAs heterojunction grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). By virtue of nonalloyed ohmic contacts as well as a sewer layer which is electrically separated from ohmic electrodes, a carrier density modulation and a strong negative differential resistance can be obtained. A peak-to-valley current ratio up to 140000 (1/spl times/10/sup 6/) at 300 (77) K are, to our knowledge, among the best for InAlAs/InGaAs structures. The proposed device also reveals sharp charge injection and broad valley range.

7 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of spacer layer thickness on two-dimensional hole gas concentration and hole mobility is also studied, and the delta-doped p-type strained InGaAs/GaAs HFET with 8 nm spacer-layer thickness exhibits extrinsic transconductances of 15 mS/mm at 300 K and 24 mS /mm at 77 K.
Abstract: Zinc-delta-doped strained quantum well InGaAs/GaAs p-channel heterostructure field-effect transistor (HFET) grown by low-pressure metalorganic chemical vapor deposition has been realized. In terms of using the zinc-delta-doping technique by interrupting the growth, high concentration is carried out. The influence of spacer layer thickness on two-dimensional hole gas concentration and hole mobility is also studied. The delta-doped p-type strained InGaAs/GaAs HFET with 8 nm spacer layer thickness exhibits extrinsic transconductances of 15 mS/mm at 300 K and 24 mS/mm at 77 K. Secondary-ion mass spectrometry (SIMS) is carried out to confirm the film quality, zinc diffusion profile and sharpness of the proposed structures. Due to the smaller mobility difference in InGaAs/GaAs than in using AlGaAs barriers, the gate voltage swing in the p-channel delta-doped InGaAs/GaAs HFET exhibits a value about 1.7 V. Consequently, a wider linear amplifier application is expected in the present device.

4 citations

Journal ArticleDOI
TL;DR: In this article, an emitter edge-thinning design is used for a lattice-matched InGaAs/InP double-heterostructure-emitter bipolar transistor (DHEBT) grown by low-pressure metalorganic chemical vapor deposition (MOCVD).
Abstract: An emitter edge-thinning design is used for a lattice-matched InGaAs/InP double-heterostructure-emitter bipolar transistor (DHEBT) grown by low-pressure metalorganic chemical vapor deposition (MOCVD). Using the emitter edge-thinning technique, the surface recombination current is reduced and the current gain is improved. This structure reveals a typical current gain as high as 120 at a collector current density of 241 A/cm2, along with an offset voltage as low as 45 mV. Furthermore, the problem of surface recombination current is also discussed in terms of the emitter size effect on current gain. The Gummel plots are shown to explain the influence of the emitter edge-thinning process on the base current ideality factor.

3 citations


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Journal ArticleDOI
TL;DR: In this article, a Pt/AlGaN/GaN Schottky diode was used to measure the current voltage and current amplitude of a relatively low concentration NH 3 /air gas.
Abstract: The interesting ammonia sensing current–voltage ( I–V ) characteristics of a Pt/AlGaN/GaN Schottky diode are firstly studied and demonstrated. It is found that the ammonia sensitivity is increased by increasing the temperature. Yet, the sensitivity is decreased when the temperature is higher than 423 K. Experimentally, the studied device exhibits a good sensitivity of 13.1 under exposing to a relatively low concentration ammonia gas of 35 ppm NH 3 /air. In addition, the good sensing performance of the studied device is demonstrated over a wide operating temperature regime from 298 K to 473 K. A highest ammonia sensing response of 182.7 is found at 423 K while a 10,000 ppm NH 3 /air gas is introduced.

31 citations

Journal ArticleDOI
TL;DR: In this article, an AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor (MOS-HEMT) using a high-k TiO2 gate insulator is demonstrated.
Abstract: An AlGaN/GaN metal–oxide–semiconductor high-electron mobility transistor (MOS-HEMT) that uses a high-k TiO2 gate insulator is demonstrated. TiO2 films are annealed at 300 °C and 600 °C in N2 or O2 following the deposition of an oxide layer. Experimental results reveal that the 300 °C N2-annealed TiO2/GaN MOS capacitor has the smallest interface traps of any of the studied devices. The 300 °C N2-annealed oxide interlayers between the GaN and the gate metal reduce the gate leakage current and improve the dc, high-frequency, and noise characteristics. The gate leakage current of the 300 °C N2-annealed MOS-HEMT is more than 3 orders of magnitude less than that of the baseline HEMT. This brief is the first to fabricate a GaN-based MOS-HEMT using an N2-annealed TiO2 gate insulator.

28 citations

Journal ArticleDOI
TL;DR: In this paper, the InGaP/GaAs heterojunction bipolar transistors (HBTs) with a sulfur-treated base layer were compared to those with a non-sulfur base layer.

26 citations

Journal ArticleDOI
TL;DR: In this article, an interesting Pt/AlGaN/GaN Schottky-type ammonia gas sensor is fabricated and studied, and both the steady and transient state behaviors of ammonia adsorption reactions are investigated.
Abstract: An interesting Pt/AlGaN/GaN Schottky-type ammonia gas sensor is fabricated and studied. Both the steady-and transient-state behaviors of ammonia adsorption reactions are investigated. At 150°C, significant ammonia detection is observed under a low ammonia concentration of 35-ppm NH3/air. Moreover, a high ammonia sensing response of 18300% and the large Schottky barrier variation ratio A.φb/φb, air of 13.8% are observed upon exposure to a 1% NH3/air gas at 150°C. The presence of dipoles at the metal-semiconductor interface leads to a lowering effect of Schottky barrier height and a larger current. In addition, based on thermodynamics, in contrast with a hydrogen adsorption reaction, the ammonia adsorption reaction is an endothermic reaction. Consequently, the studied NH3 sensor structure provides the promise to integrate high-performance AlGaN/ GaN-based optoelectronic and microwave devices on a single chip.

25 citations

Journal ArticleDOI
TL;DR: In this paper, a heteroepitaxy with large thermal and lattice mismatch between the semiconductor and substrate is considered for high-quality epitaxial growth, and high growth temperatures (>1000 °C) a...
Abstract: Heteroepitaxy with large thermal and lattice mismatch between the semiconductor and substrate is a critical issue for high-quality epitaxial growth. Typically, high growth temperatures (>1000 °C) a...

23 citations