HIGH-SPEED INGAP GAAS HBTS WITH A STRAINED INXGA1-XAS BASE/

A self-aligned InGaP/GaAs heterojunction bipolar transistor with a com positionally graded InxGa1-xAs base has been demonstrated with f(T) = 83 GHz and f(max) = 197 GHz. To our knowledge, these results are the h ighest reported for both parameters in InGaP/GaAs HBT's. The graded ba se, which improves electron transport through the base, results in a d e current gain and a cutoff frequency which are 100% and 20% higher, r espectively, than that achieved by an identical device with a nongrade d base, The high f(max) results from a heavily doped base, self-aligne d base contacts, and a self-aligned collector etch, These results demo nstrate the applicability of InGaP/GaAs HBT's in high-speed microwave applications.