Fabrication of submicron buried metal heterojunction bipolar transistor by EB-lithography

A buried metal heterojunction bipolar transistor with submicron emitter was fabricated by electron-beam lithography. Two tungsten wires of 100 nm width, 100 nm height and 200 nm period were buried in the InP collector layer for the device with an emitter area of 0.3×1.5 μm. Total base-collector capacitance was reduced to about 22% of that calculated from the physical dimensions of conventional heterojunction bipolar transistors. Current gain cutoff frequency of 82 GHz and maximum oscillation frequency of 200 GHz were obtained.