A 140 GHz f/sub max/ InAlAs/InGaAs pulse-doped InGaAlAs quaternary collector HBT with a 20 V BVceo

Although InP-based HBTs have shown excellent RF performance, the low breakdown and Early voltages of InGaAs collectors have limited their insertion into high linearity and power amplifiers. InAlAs/InGaAs NpN double-HBTs with compositionally graded quaternary InGaAlAs collectors realized a high BVceo of 20V with minimal carrier blocking up to high current densities. The same device exhibited an ft and fmax of 58 GHz and 140 GHz, respectively, which is comparable to otherwise identical InGaAs collector devices.