Light emission from the GaAs/AlGaAs HBT collector junction at breakdown

The authors report the observation of light emission from the GaAs collector-base junction of a GaAs/AlGaAs HBT (heterojunction bipolar transistor) at breakdown. The photoemission spectra of the reverse-bias junction and resolved peaks at 2.03 and 1.43 eV were measured, with the intensities dependent upon the reverse current. An experimental technique for measuring the threshold energy for impact ionization in the investigated material is reported.