Ke-Hua Su

Bio: Ke-Hua Su is an academic researcher from National Cheng Kung University. The author has contributed to research in topics: High-electron-mobility transistor & Transconductance. The author has an hindex of 6, co-authored 22 publications receiving 123 citations.

Characteristics of In/sub 0.425/Al/sub 0.575/As-InxGa/sub 1-x/As metamorphic HEMTs with pseudomorphic and symmetrically graded channels

Abstract: In/sub 0.425/Al/sub 0.575/As-In/sub x/Ga/sub 1-x/As metamorphic high electron mobility transistors (MHEMTs) with two different channel designs, grown by molecular beam epitaxy (MBE) system, have been successfully investigated. Comprehensive dc and high-frequency characteristics, including the extrinsic transconductance, current driving capability, device linearity, pinch-off property, gate-voltage swing, breakdown performance, unity-gain cutoff frequency, max. oscillation frequency, output power, and power gain, etc., have been characterized and compared. In addition, complete parametric information of the small-signal device model has also been extracted and discussed for the pseudomorphic channel MHEMT (PC-MHEMT) and the V-shaped symmetrically graded channel MHEMT (SGC-MHEMT), respectively.

Enhancing the current gain in InP/InGaAs double heterojunction bipolar transistors using emitter edge thinning

Abstract: This paper reports InP/InGaAs double heterojunction bipolar transistors (DHBTs) made with composite-collector designs. The current gains of the DHBTs without and with emitter edge-thinning designs are 125 and 180, respectively. The composition of the collector and the base currents is analysed from the Gummel plots. Experimental data demonstrate that emitter edge thinning can further reduce the surface recombination current of the InP/InGaAs DHBTs and thus dramatically improve current gain, even though the surface recombination in InP/InGaAs DHBTs is much less than in GaAs-based DHBTs.

Comparison of Al0.32Ga0.68N ∕ GaN Heterostructure Field-Effect Transistors with Different Channel Thicknesses

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.

A Novel Dilute Antimony Channel $\hbox{In}_{0.2}\hbox{Ga}_{0.8}\hbox{AsSb}/\hbox{GaAs}$ HEMT

Abstract: This letter reports, for the first time, a high-electron mobility transistor (HEMT) using a dilute antimony In0.2Ga0.8 AsSb channel, which is grown by a molecular-beam epitaxy system. The interfacial quality within the InGaAsSb/GaAs quantum well of the HEMT device was effectively improved by introducing the surfactantlike Sb atoms during the growth of the InGaAs layer. The improved heterostructural quality and electron transport properties have also been verified by various surface characterization techniques. In comparison, the proposed HEMT with (without) the incorporation of Sb atoms has demonstrated the maximum extrinsic transconductance gm,max of 227 (180) mS/mm, a drain saturation current density IDSS of 218 (170) mA/mm, a gate-voltage swing of 1.215 (1.15) V, a cutoff frequency fT of 25 (20.6) GHz, and the maximum oscillation frequency fmax of 28.3 (25.6) GHz at 300 K with gate dimensions of 1.2times200 mum2

Comparative Studies on Double δ -Doped Al0.3Ga0.7As ∕ In x Ga1 − x As ∕ GaAs Symmetrically Graded Doped-Channel Field-Effect Transistors

Abstract: This work provides comparative studies of a double δ-doped Al 0.3 Ga 0.7 As/In ℵ Ga 1-ℵ As/GaAs symmetrically graded (x = 0.15 → 0.2 → 0.15) doped-channel field-effect transistor (DD-DCFET) with respect to a conventional double 8-doped pseudomorphic high electron mobility transistor (pHEMT) and a conventional DCFET structure. All threes samples, grown by the low-pressure metallorganic chemical vapor deposition (LP-MOCVD) system, have identical layer structures except for their different doping schemes. Comprehensive investigations on the static, microwave, and temperature-dependent characteristics have been made. Possessing the advantages of DCFETs and pHEMTs, the proposed DD-DCFET has demonstrated comprehensively superior linearity, current drive, voltage gain, high-frequency characteristics, and thermal stability characteristics. It is promisingly suitable for millimeter-wave integrated circuit applications.

A Novel $\hbox{Pt/In}_{0.52}\hbox{Al}_{0.48}\hbox{As}$ Schottky Diode-Type Hydrogen Sensor

Abstract: On the basis of a Pt/In052Al048As metal-semiconductor structure, a novel hydrogen sensor is fabricated and demonstrated The studied Pt/In052Al048As Schottky diode-type hydrogen sensor exhibits significant sensing performance including high relative sensitivity ratio of about 2600% (under the 1% H2/air gas and VR=-05 V at 30 degC), large current variation of 310 muA (under the 1% H2/air gas and VR=-5 V at 200 degC), widespread reverse-voltage regime (0~-5 V), stable hydrogen-sensing current-voltage (I-V) curves, and fast transient response time of 15 s The calculated Schottky barrier-height change and series-resistance variation, from the thermionic-emission model and Norde method, are 870 meV and 288 Omega, respectively (under the 1% H2/air gas at 30 degC) The hydrogen concentrations and operating temperatures tested in this letter are in the range of 15 ppm-1% H2/air and 30 degC-250 degC, respectively Based on the excellent integration compatibility with InP-based electronic devices, the studied device provides the potentiality in high-performance sensor-array applications

Ammonia sensing characteristics of a Pt/AlGaN/GaN Schottky diode

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.

Improved AlGaN/GaN Metal–Oxide– Semiconductor High-Electron Mobility Transistors With TiO 2 Gate Dielectric Annealed in Nitrogen

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.

Performance Improvement in Tensile-Strained $hbox In_0.5hbox Al_0.5hbox As/hbox In_xhbox Ga_1-xhbox As/hbox In_0.5hbox Al_0.5hbox As$ Metamorphic HEMT

Abstract: This paper proposes a $hbox In_0.5hbox Al_0.5$ As/ $hbox In_xhbox Ga_1-xhbox As$break / $hbox In_0.5hbox Al_0.5hbox As$ $(x=0.3-0.5-0.3)$ metamorphic high-electron mobility transistor with tensile-strained channel. The tensile-strained channel structure exhibits significant improvements in dc and RF characteristics, including extrinsic transconductance, current driving capability, thermal stability, unity-gain cutoff frequency, maximum oscillation frequency, output power, power gain, and power added efficiency.