C.C. Hsu

Integration of GalnP/GaAs heterojunction bipolar transistors and high electron mobility transistors

Integration of carbon-doped GaInP/GaAs heterojunction bipolar transistors (HBTs) and high electron mobility transistors (HEMTs) is demonstrated by growing an HBT on the top of a HEMT. A current gain of 60, a cutoff frequency of 59 GHz and a maximum oscillation frequency of 68 GHz were obtained for a 5/spl times/15 /spl mu/m/sup 2/ self-aligned HBT. The HEMT, with a gate length of 1.5 /spl mu/m has a transconductance of 210 mS/mm, a cutoff frequency of 9 GHz and a maximum oscillation frequency of 22 GHz. It is shown that the GaInP/GaAs HBT on the HEMT is a simple Bi-FET technology suitable for microwave and mixed signal applications.

Comparison of GaInP/GaAs heterostructure-emitter bipolar transistors and heterojunction bipolar transistors

Carbon-doped GaInP/GaAs heterojunction bipolar transistors (HBTs) and heterostructure-emitter bipolar transistors (HEBTs) grown by MOCVD were fabricated. Experimental comparison of HBTs and HEBTs has been made based on the dc and the RF performance. HBTs have higher current gains than those of HEBTs in the high current regime, while HEBTs offer a smaller offset voltage and better uniformity in dc characteristics across the wafer. The current gain and cutoff frequency of the DEBT with a 150 /spl Aring/ emitter set-back layer are comparable to those of HBTs. DC (differential) current gains of 600 (900) and 560 (900) were obtained at a collector current density of 2.5/spl times/10/sup 4/ A/cm/sup 2/ for the HBT and HEBT, respectively. The cutoff frequencies are 37 and 31 GHz for the HBT and HEBT, respectively. It is shown that there is negligible contribution of the diffusion capacitance to the emitter capacitance in HEBTs with a thin emitter set-back layer but not with a thick emitter set-back layer. The behavior of HEBTs both in dc and RF characteristics is similar to that of HBTs. >

Low turn-on voltage InGaP/GaAsSb/GaAs double HBTs grown by MOCVD

A novel InGaP/GaAs/sub 0.92/Sb/sub 0.08//GaAs double heterojunction bipolar transistor (DHBT) with low turn-on voltage has been fabricated. The turn-on voltage of the DHBT is typically 150 mV lower than that of the conventional InGaP/GaAs HBT, indicating that GaAsSb is a suitable base material for reducing the turn-on voltage of GaAs HBTs. A current gain of 50 has been obtained for the InGaP/GaAs/sub 0.92/Sb/sub 0.08//GaAs DHBT. The results show that InGaP/GaAsSb/GaAs DHBTs have a great potential for reducing operating voltage and power dissipation.

Carbon-doped GaInP/GaAs heterojunction bipolar transistors grown by metalorganic chemical vapor deposition using nitrogen as the carrier gas

The use of nitrogen as the carrier gas in metalorganic chemical vapor deposition (MOCVD) for the growth of carbon-doped GaInP/GaAs heterojunction bipolar transistors (HBTs) is reported. The material quality grown using a nitrogen carrier gas is the same as that of using a hydrogen carrier gas. High carbon doping and hole concentrations of 3×1020 and 2×1020 cm−3 in GaAs were obtained. The fabricated HBTs showed very good DC and RF performances indicating that nitrogen can be a promising carrier gas for MOCVD growth.

Carbon doped GaInP/GaAs double heterostructure-emitter bipolar transistors with high current gain

Carbon-doped GaInP/GaAs double heterostructure-emitter bipolar transistors (DHEBTs) grown by MOCVD were fabricated. DC current gain of 430 (differential gain of 500) and an offset voltage of 25 mV were obtained. A gain up to 9 was achieved at a low collector current density of 10/sup -3/ A/cm/sup 2/. By using a 600 /spl Aring/ set-back layer in the collector, the saturation (knee) voltage was found to be lower than 2 V at a collector current density of 1/spl times/10/sup 4/ A/cm/sup 2/. A cutoff frequency of 23 GHz and a maximum oscillation frequency of 17.8 GHz were obtained. >

Surface morphology of metalorganic vapor phase epitaxy grown GaAs observed by atomic force microscopy

Steps of monolayer height (0.28 nm) are observed by atomic force microscope on a metalorganic vapor phase epitaxy grown GaAs surface. Monolayer terrace width was found to be as large as 430 nm, the same as the vicinal substrate surface. The growth mechanism is according to the classical Burton–Cabrera–Frank theory. We may have a larger (≳500 nm) terrace width and surface diffusion length if an exactly oriented [100] substrate is used.

High‐performance InP/Ga0.47In0.53As/InP metal‐semiconductor‐metal photodetectors with a strained Al0.1In0.9P barrier enhancement layer

A reduction in the dark current and an enhancement of the breakdown voltage have been observed in interdigitated InP/Ga0.47In0.53As/InP metal‐semiconductor‐metal photodetectors when a cap layer of Al0.1In0.9P was grown on the epitaxial structure to increase the Schottky barrier. The devices had a dc responsivity of 0.32 A/W and an intrinsic response faster than 74 ps.

A reliability comparison of InGaP/GaAs HBTs with and without passivation ledge

Abstract InGaP/GaAs heterojunction bipolar transistors (HBTs) with and without passivation ledge in the extrinsic base region were investigated. Gummel plot changes before and after reliability testing were compared. The experimental results demonstrated that the devices featuring the lower quality of the extrinsic base surface are more sensitive to a temperature–current stress. The HBTs with a passivation ledge have an activation energy of 1.41 eV and a mean time to failure (MTTF) of 106 h whereas the HBTs without passivation ledge have an activation energy of 1.24 eV and a MTTF of 105 h.

Temperature dependence of current gain of GaInP/GaAs heterojunction and heterostructure-emitter bipolar transistors

The temperature effect on current gain is presented for GaInP/GaAs heterojunction and heterostructure-emitter bipolar transistors (HBTs and HEBTs). Experimental results showed that the current gain of the HEBT increases with the increase of temperature in the temperature range of 25-125/spl deg/C and decreases slightly at temperatures above 150/spl deg/C. The smaller the collector current, the larger is the positive differential temperature coefficient. At high current levels, the current gain dependence on temperature is significantly reduced. On the other hand, a large negative coefficient is observed in the HBT in all current range. This finding indicates that the HEBT is a better candidate than the HBT for power devices.

High efficiency, low offset voltage InGaP/GaAs power heterostructure-emitter bipolar transistors with advanced thermal management

High efficiency, low offset voltage InGaP/GaAs power heterostructure-emitter bipolar transistors (HEBTs) have been demonstrated. The large signal performance of the HEBTs is characterized. Output power of 0.25 W with power added efficiency (PAE) of 63.5% at 1.9 GHz has been achieved from a 26-finger HEBT with total emitter area of 873.6 /spl mu/m/sup 2/. Output power of 1.0 W with PAE of 63% has been obtained from the composition of four above-mentioned power cells at the optimum conditions of impedance matching. The thermal performance of HEBT is presented and the results show better thermal management than conventional HBT. The experimental results demonstrate good power performance and capability of HEBTs.