Wen-Lung Chang

New self-aligned T-gate InGaP/GaAs field-effect transistors grown by LP-MOCVD

This paper reports on self-aligned T-gate InGaP/GaAs FETs using n/sup +//N/sup +///spl delta/(P/sup +/)/n structures. N/sup +/-InGaP//spl delta/(P/sup +/)-InGaP/n-GaAs forms a planar-doped barrier. The inherent ohmic gate of camel-gate FETs together with a highly selective etch between an InGaP and a GaAs layers offers a self-aligned T-shape gate with a reduced effective length. A fabricated device with a reduced gate dimension of 1.5/spl times/100 (0.6/spl times/100) /spl mu/m/sup 2/ obtained from 2/spl times/100 (1/spl times/100) /spl mu/m/sup 2/ gate metal exhibits an extrinsic transconductance, unity-current gain frequency, and unity-power gain frequency of 78 (80) mS/mm, 9 (19.5), and 28 (30) GHz, respectively.

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.

Temperature-dependence investigation of a high-performance inverted delta-doped V-shaped GaInP/In/sub x/Ga/sub 1-x/As/GaAs pseudomorphic high electron mobility transistor

A newly designed inverted delta-doped V-shaped GaInP/In/sub x/Ga/sub 1-x/As/GaAs pseudomorphic high electron mobility transistor (PHEMT) has been successfully fabricated and studied. For a 1/spl times/100 /spl mu/m/sup 2/ device, a high gate-to-drain breakdown voltage over 30 V at 300 K is found. In addition, a maximum transconductance of 201 mS/mm with a broad operation regime for 3 V of gate bias (565 mA/mm of drain current density), a very high output drain saturation current density of 826 mA/mm, and a high DC gain ratio of 575 are obtained. Furthermore, good temperature-dependent performances at the operating temperature ranging from 300 to 450 K are found. The unity current gain cutoff frequency f/sub T/ and maximum oscillation frequency f/sub max/ up to 16 and 34 GHz are obtained, respectively. Meanwhile, the studied device shows the significantly wide and flat gate bias operation regime (3 V) for microwave performances.

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.

Characteristics and comparison of In0.49Ga0.51P/InGaAs single and double delta-doped pseudomorphic high electron mobility transistors

Abstract The InGaP/InGaAs single and double delta-doped pseudomorphic high electron mobility transistor (δ-PHEMT) grown by low-pressure metal organic chemical vapor deposition have been fabricated and investigated. Based on the employment of the wide-gap InGaP Schottky layer and delta-doped carrier supplier, the high breakdown voltages together with good device characteristics are obtained simultaneously. Furthermore, the newly designed V-shaped InGaAs channel can enhance the carrier confinement effect and increase the product of carrier concentration and mobility. Experimentally, for 1×100 μm 2 devices, the gate-to-drain breakdown voltages larger than 40 (30) V, the transconductances of 90 (201) mS/mm, and the maximum current densities of 646 (846) mA/mm are achieved for the studied single and double δ-PHEMT, respectively. Meanwhile, the measured fT and fmax are 12 (16) and 28.4 (34) GHz, respectively.

High-performance double delta-doped sheets Ga0.51In0.49P/In0.15Ga0.85As/ Ga0.51In0.49P pseudomorphic heterostructure transistors

Novel double delta-doped sheet (D3 S) Ga0.51 In0.49 P/In0.15 Ga0.85 As/Ga0.51 In0.49 P pseudomorphic high-electron-mobility transistors (PHEMTs) have been fabricated successfully and studied. A wide-gap Ga0.51 In0.49 P Schottky layer and a D3 S structure are used to improve device performance. Furthermore, an airbridge-gate structure is employed to achieve good dc and RF performances. For a 1 µm gate length device, a high gate-to-drain breakdown voltage over 35 V, an available output current density up to 615 mA mm-1 , a maximum transconductance of 110 mS mm-1 and a high dc gain ratio of 487 are obtained. On the other hand, the maximum values of unity current gain cut-off frequency fT and maximum oscillation frequency fmax are 19.5 and 40.5 GHz, respectively. The output power of 15.6 dB m (363 mW mm-1 ), power gain of 5.6 dB, power added efficiency (PAE) of 37% and drain efficiency (DE) of 51% are obtained at an input power of 10 dB m and the measured frequency of 2.4 GHz.

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.