A Study Of GaAs Inversion-Base Bipolar Transistor

Abstract

Heterostructure bipolar transistor (HBT) theory and technology have been comprehensively reviewed by Kroemer [ l ] . the structures studied lby many researchers in various laboratories [for example, see Ref 2 and 3 1 . For microwave application, f of 75 GHz have been demonstrated [2]. Common emitter current gain as high as 2000 has also been reported [ 3 ] . One of the possible approaches to achieve higher frequency performance of an HBT is to reduce the base width. To obtain a thin base, Matsumoto et. al. [ 4 ] proposed an AlAs/GaAs heterostructure in a bipolar transistor to obtain an "inversion base" (hence the name inversion-base bipolar transistor (IBT)). In this structure the base is formed by a two dimensional hole gas created via inversion at the heterointerface. The potential advantages of an IBT are the reduced base width and ease of fabrication. Current gains of 17.1 and 5.6 were obtained at 300 K and 77 K respectively [ 4 ] . It was suggested that the increased current gain at 300 K relative to 77 K may be due to the increase of t$e thermally stimulated electrons which go over the AlAs barrier from the n GaAs emitter to the nGaAs collector. which resulted in demonstrating bipolar transistor action with much improved device performance in terms of current gain and density. The AlGaAs/GaAs HBT is one of