INFLUENCE OF SUBSTRATE MISORIENTATION ON CURRENT GAIN IN ALGAAS/GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS GROWN BY METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION

The influence of substrate misorientation on the current gain characteristics of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) is systematically investigated. The current gain is found to increase by a factor of up to three when the substrate is tilted from (100). The behavior of the minority electron lifetime determined separately in thick C-doped GaAs layers grown on the same set of misoriented substrates correlates very well with that of the current gain. This is consistent with the result of base current ideality factors, which are close to unity for all devices. These improvements in the current gain and the minority electron lifetime are commonly observed in layers grown on misoriented substrates regardless of the substrate misorientation direction. These results can be interpreted in terms of the incorporation of nonradiative recombination centers such as native defects, where the substrate misorientation can effectively supress the formation of these centers.