Space-charge recombination in N-AlGaAs/p+-GaAs heterojunction diodes

Space-charge recombination currents were measured in N-AlGaAs/p+-GaAs heterojunction diodes grown by molecular beam epitaxy (MBE) under various growth conditions. The diode epilayer structure was designed to simulate the emitter-base junction of a heterojunction bipolar transistor.The diodes were fabricated using a fast turnaround mesa process, and their forward current-voltage characteristics were fit to a simple model to extract the recombination current density. The space-charge recombination decreased steeply with increasing growth temperature Ts between 560 and 610 °C, and it decreased when the As4/Ga ratio was reduced from 3 to 1. It was lower for misoriented substrates (6° off 〈100〉 toward 〈111〉A) than for 〈100〉 oriented substrates, and it decreased significantly as the result of a post-growth anneal in the MBE system.