Beryllium doped InP/InGaAsP heterojunction bipolar transistors

Heterojunction bipolar transistors with InP emitters and In0.72Ga0.28As0.61P0.39 (lambda = 1.3 mu m) base and collector layers were fabricated. Their performance was compared to conventional InP/InGaAs HBTs. The layers were grown by metal-organic molecular beam epitaxy. The base was beryllium doped. Secondary ion mass spectroscopy analysis revealed that the upper limit of useful Be doping level in the base was about 1 x 10(19) cm(-3). At higher doping levels considerable redistribution in depth of Be was observed. The electron impact ionization coefficient in InGaAsP was extracted from the device characteristics. The anomalous electric field and temperature dependence of impact ionization found in InGaAs was not observed in InGaAsP. The breakdown voltage of the devices with an InGaAsP collector was considerably larger than in devices with an InGaAs collector. (C) 1998 Elsevier Science Ltd. All rights reserved.