InP/GaAsSb/InP DHBTs with high f/sub T/ and f/sub MAX/ for wireless communication applications

We study the DC and microwave performance of MOCVD-grown carbon-doped InP/GaAsSb/InP double heterojunction transistors (DHBTs) with high cut-off frequencies. A maximum cutoff frequency of 106 GHz is obtained while maintaining a relatively high breakdown voltage (BV/sub CEO/=8 V) in devices with a 2000 /spl Aring/ InP collector. In these devices, the maximum frequency of oscillation is limited by the GaAsSb base sheet resistance (which is high in comparison to GaAs or GaInAs conventional bases), and high f/sub MAX/ values can only be achieved by scaling the devices to simultaneously reduce the total base resistance R/sub B/ and the base-collector capacitance C/sub BC/. A new self-aligned process was developed which results in f/sub T/=80 GHz and C/sub BC/=90 GHz for devices with a 3000 /spl Aring/ collector and a 1 /spl mu/m emitter stripe fabricated by contact lithography and all-wet etching.