POWER PERFORMANCE OF InGaAs/InP SINGLE HBTs

Impressive microwave results have been published for both Single(SHBT) and Double(DHBT) Heterostructure Bipolar Transistors based upon the InP material system. InP-based SHBTs have been reported to have excellent high-frequency performances such as unity current-gain frequency (fT) of 200 GHz (1) and maximum oscillation frequency (fmax) of 236 GHz (2). The best results for InP-based DHBTs include fT of 160 GHz (3) and fmax of 267 GHz (4). Most data published on the power performance of InP-based HBTs so far has concentrated on DHBTs. Due to the wide-bandgap collector, InP DHBTs typically have a higher breakdown voltage and hence can produce higher levels of output power. Recent reports on InP-based DHBTs include 5.3 W/mm of output power at a power-added efficiency (PAE) of 62% from ten 2×30-μm emitters under class B operation (5). Typically, the microwave power characteristics of InP/InGaAs SHBTs has not been addressed due to their relatively inferior DC characteristics when compared to DHBTs, which implies early breakdown and thus limited power performance. On the other hand, SHBTs are very attractive for higher frequency applications due to the absence of the heterojunction spike at the base-collector (B-C) interface. Moreover, the homojunction B-C structure offers direct compatibility for HBT integration with PIN diodes, since the latter can be realized by using the B-C-subcollector region. Such integration is needed not only for OEICs but also for MMICs with switching capabilities, as recently reported by the authors (6). This paper reports for the first time a systematic investigation of InP-based SHBT characteristics and demonstrates their suitability for power applications.