Metamorphic InP/InGaAs double-heterojunction bipolar transistors on GaAs grown by molecular-beam epitaxy

InP/InGaAs double-heterojunction bipolar transistor (HBT) structures were grown metamorphically on GaAs substrates by solid-source molecular-beam epitaxy. A linearly graded InxGa1-xP (x varying from 0.48 to 1) buffer layer was used to accommodate the strain relaxation. The crystallinity of the buffer layer and the HBT structure was examined by x-ray diffractometry. Devices with 5 x 5 mu m(2) emitter area showed a typical peak current gain of 40, a common-emitter breakdown voltage (BVCEO) higher than 9 V, a current gain cut-off frequency (f(T)) of 46 GHz, and a maximum oscillation frequency (f(max)) of 40 GHz. (C) 2000 American Institute of Physics. [S0003-6951(00)02432-3].