SURFACE RECOMBINATION CURRENT IN INGAP GAAS HETEROSTRUCTURE-EMITTER BIPOLAR-TRANSISTORS

The behavior of the surface recombination current was examined in InGaP/GaAs heterostructure-emitter bipolar transistors (HEBT's) with both exposed GaAs surface and InGaP passivated surface based on the emitter-size effect on current gain. The results indicate that the GaAs surface recombination current has a 1 kT-like dependence in the high current regime and a 2 kT-like dependence in the low current regime which is similar to published experimental results in AlGaAs/GaAs and InGaP/GaAs HBT's. The surface recombination current in devices with an InGaP passivation layer has an order of magnitude lower value in low current regime and more than two orders lower in high current regime than that in devices with exposed GaAs surface.