High-speed InGaP/GaAs HBTs with a strained In/sub x/Ga/sub 1-x/As base

A self-aligned InGaP/GaAs heterojunction bipolar transistor with a compositionally graded In/sub x/Ga/sub 1-x/As base has been demonstrated with f/sub T/=83 GHz and f/sub max/=197 GHz. To our knowledge, these results are the highest reported for both parameters in InGaP/GaAs HBT's. The graded base, which improves electron transport through the base, results in a DC current gain and a cutoff frequency which are 100% and 20% higher, respectively, than that achieved by an identical device with a nongraded base. The high f/sub max/ results from a heavily doped base, self-aligned base contacts, and a self-aligned collector etch. These results demonstrate the applicability of InGaP/GaAs HBT's in high-speed microwave applications.