Jing-Yuh Chen

Amorphous silicon/silicon carbide superlattice avalanche photodiodes

An a-Si/SiC:H superlattice avalanche photodiode (SAPD) has been successfully fabricated on an ITO/glass substrate by plasma-enhanced chemical vapor deposition. The room-temperature electron and hole impact ionization rates, alpha and beta , have been determined for the a-Si/SiC:H superlattice structure by photocurrent multiplication measurements. The ratio alpha / beta is 6.5 at a maximum electric field of 2.08*10/sup 5/ V/cm. Avalanche multiplications in the superlattice layer yields an optical gain of 184 at a reverse bias V/sub R/=20 V and an incident light power P/sub in/=5 mu W. An LED-SAPD photocouple exhibited a switching time of 4.5 mu s at a load resistance R-1.8 k Omega . >

A novel Pd/oxide/GaAs metal-insulator-semiconductor field-effect transistor (MISFET) hydrogen sensor

A novel and high-performance Pd/oxide/GaAs hydrogen sensor based on a metal-insulator-semiconductor field-effect transistor (MISFET) is fabricated and studied. In the presence of the interfacial oxide, high sensitivity and significant increase in output drain current are observed. In the presence of hydrogen, a 2×200 µm2 gate dimension device shows good dc characteristics including high turn-on voltage, an obvious variation of drain current and a short response time. In addition, under the applied voltage of -4 V and 537 ppm hydrogen in air, a very high sensitivity of 9473 is obtained. This performance shows that the device studied has a good potential for high-speed and high-sensitivity hydrogen sensor and MISFET integrated circuit applications.

High-performance InGaP/In x Ga/sub 1-x/As HEMT with an inverted delta-doped V-shaped channel structure

This letter reports a new and high-performance InGaP/In/sub x/Ga/sub 1-x/As high electron mobility transistor (HEMT) with an inverted delta-doped V-shaped channel. Due to the presence of V-shaped inverted delta-doped InGaP/In/sub x/Ga/sub 1-x/As structure, good carrier confinement and a flat and wide transconductance operation regime are expected. Experimentally, the fabricated device (1/spl times/100 /spl mu/m/sup 2/) shows a high gate-to-drain breakdown voltage of 30 V and a high output drain saturation current density of 826 mA/mm at V/sub GS/=2.5 V. The high transconductance expands over a very broad operation range with the maximum value of 201 mS/mm at 300 K. Meanwhile, the studied device exhibits a good microwave frequency linearity.

Temperature-dependent investigation of a high-breakdown voltage and low-leakage current Ga/sub 0.51/In/sub 0.49/P/In/sub 0.15/Ga/sub 0.85/As pseudomorphic HEMT

We reported a newly designed double delta-doped GaInP/InGaAs pseudomorphic HEMT with high temperature-dependent performances. In addition to the novel aspects of the proposed HEMT structure, temperature-dependent behaviors including a high-voltage (40 V) and a low-leakage current (17 nA/mm) are further improved by eliminating mesa-sidewall effect. We obtained nearly current-independent transconductance in the temperature of 300-450 K. The measured current gain cutoff frequency f/sub T/ and maximum oscillation frequency f/sub max/ for a 1-/spl mu/m gate device are 12 and 28.4 GHz, respectively.

Application of selective removal of mesa sidewalls for high-breakdown and high-linearity Ga0.51In0.49P/In0.15Ga0.85As pseudomorphic transistors

High-linearity Ga0.51In0.49P/In0.15Ga0.85As pseudomorphic high electron-mobility transistors have been successfully fabricated and demonstrated in both direct-current and alternating-current performance. Together with a wide-gap Ga0.51In0.49P gate insulator, a gate-to-drain breakdown voltage of 33 V is further improved to over 40 V by selectively removing mesa sidewalls. The transconductance and current density of a 1×100 μm2 device at room temperature (77 K) are 90 (120) mS/mm and 646 (780) mA/mm, respectively. The measured fT and fmax are 12 and 28.4 GHz, respectively. These are consistent with 1 μm gate devices when the parasitic capacitance is reduced by selectively removing mesa sidewalls.

DC characterization of an InP-InGaAs tunneling emitter bipolar transistor (TEBT)

The dc performances of a novel InP-InGaAs tunneling emitter bipolar transistor (TEBT) are studied and demonstrated. The studied device can be operated under an extremely wide collector current regime larger than 11 decades in magnitude (10/sup -12/ to 10/sup -1/ A). A current gain of 3 is obtained even operated at an ultralow collector current of 3.9/spl times/10/sup -12/ A (1.56 /spl times/10/sup -7/ A/cm/sup 2/). The common-emitter and common-base breakdown voltages of the studied device are higher than 2 and 5 V, respectively. Furthermore, a very low collector-emitter offset voltage of 40 mV is found. The temperature-dependent dc characteristics of the TEBT are measured and studied. Consequentially, based on experimental results, the studied device provides the promise for low-power electronics applications.

Comprehensive study of InGaP/AlxGa1-xAs/GaAs heterojunction bipolar transistors with different doping concentrations of AlxGa1-xAs graded layers

The performances of InGaP/AlxGa1−xAs/GaAs heterojunction bipolar transistors (HBTs) with different doping concentrations of AlxGa1−xAs graded layers are theoretically studied. The use of the AlxGa1−xAs graded layer plays a key role in affecting the direct current and radio frequency performances of the studied HBTs. It is found that the studied devices with suitable doping concentrations of AlxGa1−xAs graded layers exhibit lower offset voltages, saturation voltages, and base and collector current ideality factors. Furthermore, due to the use of proper doping concentrations of AlxGa1−xAs graded layers, the studied devices show high values of the unity current gain cut-off frequency (fT) and maximum oscillation frequency (fmax). It is known that, from the theoretical analysis, the appropriate doping concentration of the AlxGa1−xAs graded layer is 1 × 1016 to 1 × 1018 cm−3. Consequently, this work is promising for device engineers to design high-performance HBT structures.

Multiple-route and multiple-state current-voltage characteristics of an InP/AlInGaAs switch for multiple-valued logic applications

A novel multiple-state switching device based on an InP/AlInGaAs heterojunction bipolar transistor (HBT) structure has been successfully fabricated and demonstrated. The common-emitter current gain up to 25 is obtained under the forward operation mode. However, the anomalous multiple-negative-differential-resistance (MNDR) phenomena controlled either by electrical or optical input signals are observed under the inverted operation mode. The studied device exhibits a single-route S-shaped NDR behavior in the dark and a distinct significant S-shaped MNDR phenomena by introducing an incident light source at room temperature. Moreover, the anomalous multiple-route and multiple-step current-voltage (I-V) characteristics are also observed at 77 K. The switching behaviors are attributed to the avalanche multiplication, barrier lowering effect and potential redistribution process. Experimental results show that the studied device provides a good potentiality for multiple-valued logic and optoelectronic switching system applications.

Applications of an In0.53Ga0.25Al0.22As/InP continuous-conduction-band structure for ultralow current operation transistors

Based on the compositional dependence on the conduction band discontinuity, a significant heterojunction bipolar transistor (HBT) with a continuous conduction band heterointerface between the InP emitter and the In0.53Ga0.25Al0.22As base is fabricated. Experimentally, due to the elimination of the potential spike, a very low offset voltage of 50 mV is observed. Also, the studied device exhibits better breakdown characteristics and lower output conductance as compared with other InP/InGaAs or AlInAs/InGaAs HBTs. Furthermore, attributed to the enhancement of the hole confinement by an inserted δ-doped sheet at the emitter–base interface, a dramatic current gain about 4 is found even under an ultralow current operation regime (IC⩽5 nA).

Influence of the -doping sheet and setback layer on the performance of an InGaP/GaAs heterojunction bipolar transistor

In this paper, we demonstrate the qualitative influence of a -doping sheet and setback layer on the performance of an InGaP/GaAs heterojunction bipolar transistor (HBT). The results of a theoretical simulation show that the potential spike is reduced by the simultaneous employment of an appropriate setback layer and -doping sheet. Due to the reduction in the potential spike, a high current gain, even at a small collector current regime, and small offset voltage can be attained. Experimentally, an offset voltage as small as 55 mV and current gain of 11 at collector current of A are obtained without a passivation structure.