Thermal and bias stabilities of InP/InGaAs composite-collector DHBT

Abstract

This study proposes composite-collector double heterojunction bipolar transistors (CC-DHBTs) made by low-pressure metamorphic organic chemical vapor deposition (LP-MOCVD). Both V-shaped behaviors (observed in dc current gain, β, against collector current, IC, and in offset voltage, VCE,offset, against base current, IB, plot) of the asymmetric CC-DHBT are studied. At high IC, the presented CC-DHBTs improve the dc current gain temperature stability relative to most HBTs described in the literature. Additionally, unlike that of the abrupt DHBTs in the literature, the β of the CC-DHBTs is independent of VCB, suggesting that the effect of the conduction-band barrier in the base-collector junctions may haven been eliminated. An analytical expression for the variation of VCE,offset with IB has been developed. Additionally, unlike that of the unpassivated and SiNx-passivated devices, the β of the sulfur-treated device is fairly constant over five decades of IC. The difference betreen these variously treated devices is remarkable. X-ray photoelectron spectroscopy was applied to study InGaAs surfaces that were (NH4)2Sx and SiNx passivated. The results demonstrate that passivation effectively suppresses the oxidation of As.