Reproducible fabrication of high-performance GaAs permeable base transistors

Secondary ion mass spectrometry (SIMS) analysis has been extensively used to study impurity contamination and dopant incorporation in the fabrication procedures for the permeable base transistor (PBT). As a result of these SIMS findings, the fabrication procedures have been modified to minimize contamination, and recent PBT microwave performance and wafer-to-wafer reproducibility have improved dramatically. Seven of eight recent wafers tested at microwave frequencies have yielded devices with extrapolated values of maximum frequency of oscillation (fmax) from 108 to 223 GHz, with devices from the other wafer having an extrapolated fmaxvalue of 50 GHz. The highest values obtained for maximum stable power gain were 21.3 dB at 18 GHz in one device and 14.1 dB at 26.5 GHz in another. These gains are better than or comparable to those of the best submicrometer-gatelength HEMTs and MESFETs reported to date.