Fabrication and characterization of high-performance InP/InGaAs double-heterojunction bipolar transistors

Abstract

This paper is on high-performance InP/InGaAs double-heterojunction bipolar transistors (DHBT's) utilizing compositionally step-graded InGaAsP layers between the InGaAs base and InP collector to suppress the current blocking effect. These DHBT's exhibit current gains of 200 and excellent breakdown behavior. Moreover, the DHBT's permit collector current density levels J/sub C/ up to 3/spl times/10/sup 5/ A/cm/sup 2/ at V/sub CE/=1.5 V. A current gain cutoff frequency of 155 GHz and a maximum oscillation frequency of 90 GHz have been successfully obtained at J/sub C/=1.6/spl times/10/sup 5/ A/cm/sup 2/. We have also investigated electron transport properties in the InP collector using a set of DHBT's with different injection energies into the InP collector. By increasing the injection energies, electron velocity is found to decrease from 3.5/spl times/10/sup 7/ cm/s to 1.6/spl times/10/sup 7/ cm/s, due to increased population of upper valleys. This result clearly demonstrates the significant role of nonequilibrium /spl Gamma/-valley transport in determining the high-speed performance of InP/InGaAs DHBT's.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>