COMPARISON OF IN0.5GA0.5P/GAAS SINGLE-HETEROJUNCTION AND DOUBLE-HETEROJUNCTION BIPOLAR-TRANSISTORS WITH A CARBON-DOPED BASE

A comparison of MOCVD-grown, n-p-n In0.5Ga0.5P/GaAs single- and double-heterojunction bipolar transistors (SHBT's and DHBT's, respectively) with a carbon-doped base is presented. A base doping level of 2.5 x 10(19) cm-3 was employed in both device structures, resulting in a base sheet resistance of 500 OMEGA/sq. Common-emitter current gains as high as 210 and 150 were measured for the SHBT's and DHBT's, respectively. Results of a dc performance optimization study indicate that a 15- to 25-angstrom undoped set-back layer at the emitter-base junction provides optimal common-emitter current gain. The DHBT's exhibited a 40% improvement in common-base breakdown voltage compared to SHBT's (25 versus 18 V), indicating that In0.5Ga0.5P/GaAs DHBT's may prove suitable for power device applications.