Comparison of design features and characteristics of planar and mesa diffused germanium microwave transistors

This paper presents the design and characteristics of a planar epitaxial diffused germanium microwave transistor. The device was designed to be electrically and mechanically interchangeable with a germanium mesa microwave transistor which has an extrapolated unity gain frequency (ft) of approximately 3 gigacycles. A description of the process technology used to fabricate a planar device with performance characteristics in this region will be given. The mounting and package features that provide device terminations which enable the performance inherent in the device element to be more fully utilized will be described. Consideration will also be given to mechanical and electrical reliability problems.