Effect of bulk recombination current on the current gain of GaAs/AlGaAs heterojunction bipolar transistors in GaAs-on-Si

The effect of bulk recombination current on the current gain of heterojunction bipolar transistors (HBTs) in GaAs-on-Si has been studied. A thin AlGaAs emitter layer is used to prevent an exposed extrinsic base region, which has previously masked the effect of the bulk recombination current on the current gain in HBTs. It is found that once the surface recombination current is removed, the current grain due to bulk recombination alone is approximately ten times lower for the HBTs in GaAs-on-Si than for HBTs in GaAs. The difference in the current gain is probably due to electrically active dislocations in the base in the HBTs in GaAs-on-Si, where the density is about 10/sup 8/ cm/sup -2/ as measured by transmission electron microscopy.<
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