InP/GaAsSb/InP DHBTs with f _T = 300 GHz and high maximum oscillation frequencies: the effect of scaling on device performance

Abstract

The overall microwave performance of heterostructure bipolar transistors (HBTs) depends on transistor feature sizes, and in particular on the collector to emitter area ratio. Whereas several properties associated with the InP/GaAsSb material system would suggest that NpN InP/GaAsSb/InP DHBTs should scale very well, initial results in aggressively scaled devices defined by electron beam lithography led to depressed maximum oscillation frequencies such that f MAX << f T . In the present work we report the first results achieved at SFU for devices patterned by electron beam lithography: our DHBTs are based on standard uniform layers (i.e. structures do not incorporate any performance-enhancing schemes such as compositional or impurity gradients) so as to establish performance benchmarks in the development of a new generation of epitaxial layers for aggressively scaled InP/GaAsSb DHBTs. We show that attractive performance levels are attainable in well-scaled devices based on nonetheless simple epitaxial structures.