Current prospects for the permeable base transistor

Abstract

The permeable base transistor (PBT) is a new device which is predicted to operate at higher frequencies than any other three-terminal device. In addition to its applications for microwave amplification, the PBT may be useful in very high speed, digital logic circuits. The very small dimensions of the base structure and the requirement for embedding the base metallization in a semiconductor have necessitated the development of a great deal of new technology over the past six years. The greatest effort on the GaAs device has been to achieve controlled impurity levels and low defect densities in the epitaxial process used to embed the metal. A number of different embedding techniques have been used and extensively analyzed using secondary ion mass spectrometry (SIMS). The best device result achieved with the GaAs PBT is an extrapolated maximum frequency of oscillation ( f max) exceeding 100 GHz, and that achieved with a silicon PBT is an f max of 30 GHz. Both of these results are comparable with the best results obtained with any high-frequency transistor.