The microwave silicon permeable base transistor

Silicon permeable base transistors (SiPBTs) have been fabricated, exhibiting a maximum available gain at 2 GHz of 11 dB and a 6 dB/octave decrement leading to a maximum frequency of oscillation (fmax) of 10 GHz. These SiPBTs differ in structural detail from GaAs PBT devices previously reported in that the active region does not require an epitaxial overgrowth process to encapsulate the base grating. By using x-ray lithography and reactive-ion etching, a straight-walled etched-groove structure is used to delineate collector and base regions of the device. Although design considerations were not optimized for high frequency performance in these initial devices, the results compare favorably with Si bipolar microwave transistors. With process and design optimization this performance should be enhanced substantially.