Surface passivation effects of As2S3 glass on self-aligned AlGaAs/GaAs heterojunction bipolar transistors

Abstract

A recently developed As₂S₃ chemical treatment was used to passivate the perimeters of self‐aligned heterojunction bipolar transistors (HBTs). The As₂S₃ chemical treatment significantly lowered the base current resulting in a two order of magnitude reduction in the collector current density at which dc current gain was observed (β=1). No degradation with time has been observed in the electrical characteristics of the chemically treated HBTs. This absence of degradation is attributed to the impermeability to oxygen of the As₂S₃ glass which coats the perimeter of the HBT after chemical treatment.