Observation of the Surface Recombination Current with an Ideality Factor of Unity in AlGaAs/GaAs Heterojunction Bipolar Transistors

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Abstract
The surface recombination current with an ideality factor of unity was clearly observed in AlGaAs/GaAs abrupt heterojunction bipolar transistors (HBTs) with the uniform base structure. This was derived from the difference in the base current of HBTs with and without a surface passivation layer of depleted AlGaAs. It had a linear dependence on the emitter mesa perimeter and had no component with an ideality factor of two even at a low base-emitter bias. The results were explained by a simple analysis assuming a high surface recombination velocity.