GaInP/AlGaAs/GaInP double heterojunction bipolar transistors with zero conduction band spike at the collector

Al/sub 0.11/Ga/sub 0.89/As was used in the base, next to the GaInP collector of a DHBT, to eliminate the conduction band spike. The DHBT's demonstrated high breakdown voltages, BV/sub CEO/ and BV/sub CBO/ of 44.5 V and 54.5 V (gain/spl ap/20), respectively, for a 1-/spl mu/m-thick collector doped to 2/spl times/10/sup 16/ cm/sup -3/ with no voltage dependence of the current gain. Magneto-transport measurements were made on the AlGaAs bases and indicated limitations on the maximum practical base doping due to the inferior minority electron mobility and lifetime when compared with equivalently doped GaAs. Grading in the base from Al/sub 0.11/Ga/sub 0.89/As at the collector to Al/sub 0.21/Ga/sub 0.79/As at the emitter introduced a quasielectric field in the base, reduced the base transit time by a factor of /spl sim/2.5, and improved the gain over ungraded devices with the same average Al concentration.