Photoluminescence analysis of C-doped npn AlGaAs/GaAs heterojunction bipolar transistors

We report the observation of distinct photoluminescence (PL) emission peaks at 10 K from the collector, base, emitter, and the emitter-base interface of C-doped npn heterojunction bipolar transistors (HBT). A calibration of the bandgap reduction, measured from PL versus hole density, was used for a novel determination of the base hole density in the range of 10¹⁹-10²⁰ cm⁻³. In addition, we show physically significant correlations between the other PL emission peaks and key electrical properties of the HBT. We also report the application of capacitance-voltage and deep-level transient spectroscopy for quantitative analysis of the AlGaAs emitter.