Abstract
Micro-photoreflectance (micro-PR) is performed on patterned type II InGaAlAs/GaAsSb/InP heterojunction bipolar transistor to locally measure the built-in electric fields. The results show that the efficiency of the electric field modulation correlates with the ideality factor extracted from the electrical characteristics (Gummel characteristics). The Franz-Keldysh oscillations (FKO) completely disappear at the emitter/base heterojunction on devices with high ideality factor (nearly 2), whereas typical FKO spectra are seen on samples with ideality factor ∼1. Such behavior is attributed to the type II recombination across the InGaAlAs/GaAsSb interface which can reduce the photovoltage effect. Prior to the micro-PR experiments, photoluminescence is performed to demonstrate that the InGaAlAs/GaAsSb interface nature is of type II as well as to estimate the band offset discontinuity ΔEC.
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