Yung-Hsin Shie

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.

Application of δ-doped wide-gap collector structure for high-breakdown and low-offset voltage transistors

An In0.5Ga0.5P/GaAs double heterojunction bipolar transistor with a δ-doped wide-gap collector structure has been fabricated and studied. Experimental results show that this device exhibits the advantages of a small offset voltage of 50 mV, a small saturation voltage of 1 V, and a large breakdown voltage of 20 V with a current gain of 20. These good characteristics are mainly due to the complete elimination of potential spike at emitter–base and base–collector heterojunctions. Consequently, the studied device shows a good promise for high-speed, high-power, lower-power consumption and large input signal circuit applications.

On the --- high breakdown voltage field-effect transistor

A newly designed n-GaAs camel-type field-effect transistor (CAMFET) with a triple-step doped channel has been successfully fabricated and demonstrated. Experimentally, the high gate turn-on voltage of 1.6 V and breakdown voltage of 40 V and the very low gate leakage current of are obtained for the studied CAMFET. In addition, good transistor properties are obtained. The measured current gain cut-off frequency and the maximum oscillation frequency for a m gate device are 17 and 31 GHz, respectively. Based on experimental results, the studied device shows promise for circuit applications.

Investigation of InGaP/GaAs double-delta-doped heterojunction bipolar transistor

The double-delta-doped heterojunction bipolar transistor is successfully fabricated with improved current-voltage characteristics by employing the insertion of delta-doped sheets at emitter-base (E-B) and base-collector (B-C) heterojunction. Because of the use of delta-doped sheets, the potential spikes at E-B and B-C heterojunction are suppressed substantially. Thus a higher emitter injection efficiency (current gain) and a lower knee voltage are obtained. From experimental results, it is shown that the studied device is a good candidate for high-speed and high-power circuit applications.

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.

Investigation of an InGaP GaAs resonant-tunneling transistor (RTT)

Abstract A new InGaP/GaAs resonant-tunneling transistor (RTT) has been fabricated successfully and demonstrated. A 5-period InGaP/GaAs superlattice is used as a confinement barrier for holes and an RT route for electrons. A transistor action with a common-emitter current gain up to 220 and an offset voltage of 85 mV are obtained. Due to the RT effect within the 5-period superlattice near the emitter–base p–n junction region, the N-shaped negative-differential-resistance (NDR) phenomena are observed at room temperature. Furthermore, the N-shaped NDR is found both in the saturation and forward-active region. The widely operating regime of NDR may provide the potential for practical applications.

Investigation of GaAs-based heterostructure–emitter bipolar transistors (HEBTs)

Abstract In this paper, we will investigate three GaAs-based heterostructure-emitter bipolar transistors (HEBTs). These HEBTs have different heterostructure-confinement material systems, e.g., Al0.5Ga0.5As/GaAs, In0.49Ga0.51P/GaAs, and Al0.45Ga0.55As/In0.2Ga0.8As/GaAs. For the studied devices, an n-GaAs emitter layer inserted between the confinement and base layer is expected to eliminate the potential spike at emitter–base (E–B) junction. Therefore, the low collector–emitter offset voltage (ΔVCE) is obtained. For the AlGaAs/GaAs HEBT, experimental results show that a current gain of 180 and a low offset voltage of 80 mV are acquired. In addition, for the InGaP/GaAs HEBT, the current gain is only 60 attributed to the use of larger emitter layer thickness (700 A) which causes a large recombination current in neutral-emitter regime even when a large valence band discontinuity to conduction band discontinuity ratio (ΔEv/ΔEc) is presented. On the other hand, for the AlGaAs/InGaAs/GaAs HEBT, the ΔEv value can be enhanced due to the insertion of InGaAs quantum well (QW) between the n-GaAs emitter and the p+-GaAs base layer. Thus, the confinement effect of minority carriers is enhanced and a current gain of 280 is obtained, simultaneously. Consequently, our studied devices will provide a good promise for the transistor design and circuit applications.

A new GaInP/GaAs high-barrier gate and tri-step doped channel transistor

A high-barrier gate GaInP/GaAs doped channel field-effect transistor (DCFET) has been fabricated and studied. The /spl delta/(P/sup +/)GaInP layer is employed to offer a high conduction band offset for a good electron confinement and achieve a high valance band offset as a hole barrier. The active channel is triple-step doped to obtain high-barrier camel gate. A fabricated n/sup +/-GaAs//spl delta/(P/sup +/)GaInP/n-GaAs camel diode exhibits a barrier height larger than 1.2 eV and a very high breakdown voltage of 33 V. The measured transconductance is 140 mS/mm with a unity current gain frequency of 17 GHz for a 1/spl times/50 /spl mu/m/sup 2/ device.

A new InGaP-GaAs double delta-doped heterojunction bipolar transistor (D/sup 3/HBT)

The double delta-doped heterojunction bipolar transistor (D/sup 3/HBT) is successfully fabricated with improved current-voltage characteristics by employing the insertion of delta-doped layers at the emitter-base (E-B) and base-collector (B-C) heterojunction. Due to the use of delta-doped layers, the potential spikes at the E-B and BC heterojunctions are suppressed substantially. Thus a higher emitter injection efficiency (current gain) and a lower knee voltage are obtained. From the experimental results, it is shown that the studied D/sup 3/HBT device is a good candidate for high-speed and high-power circuit applications.