Abstract
We have fabricated InGaAs/InP based DHBTs for high speed circuit applications. A process involving both wet chemical and ECR plasma etching was developed. Carbon was employed as the p-type dopant of the base layer for excellent device stability. Both the emitter–base and base–collector regions were graded using quaternary InGaAsP alloys. The extrinsic emitter–base junction is buried for junction passivation to improve device reliability. The use of an InP collector structure with the graded region results in high breakdown voltages of 8-10 V, with no current blocking. The entire structure is encapsulated with spin-on-glass. These devices show no degradation in d.c. characteristics after operation at an emitter current density of 90 kA cm −2 and a collector bias, V CE, of 2 V at room temperature for over 500 h. Typical common emitter current gain was 50. An f t of 80 and f max of 155 GHz were achieved for 2×4 μm 2 emitter size devices.
Published Version
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