| Summary: | 碩士 === 國立中央大學 === 電機工程研究所 === 99 === InP-based heterojunction bipolar transistors (HBTs) with antimonide (Sb) content in the base, such as GaAsSb and InGaAsSb, have received a great deal of attention because of their excellent dc and microwave performance associated with type-II band alignment at the base/collector (B/C) junction. However, the reliability issues associated with the Sb-containing base have not been well studied to date.
In this work, the effects of current stress on the electrical characteristics of HBTs with a highly beryllium (Be)-doped InGaAsSb base were investigated. Devices with an emitter size of 1×10 ?m2 were fabricated by a triple mesa wet-etching process. The stress current density used in this work was either 150 or 300 kA/cm2. To accelerate device degradation, current stress was performed at a junction temperature of 200 and 250 ℃. The collector currents for all the InGaAsSb base HBTs show parallel shifts toward higher base/emitter voltage after the stress. The unchanged collector ideality factors and junction capacitances imply that there were no Be out-diffusion at the junctions, thereby indicating the strength of InGaAsSb base HBTs for higher current density operations.
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