Forward and Reverse Tunnel Currents in Gallium Phosphide Diffused p-n Junctions

The current-voltage characteristics of zinc-diffused and beryllium-diffused p-n junctions in gallium phosphide have been studied at temperatures between 77° and 300°K. The dominant forward current over most of the bias range for the zinc-diffused diodes varied as exp (βV+γT), where β and γ are relatively independent of temperature and voltage. This current was shown to be qualitatively consistent with a simple tunneling model involving states in the forbidden gap. For high bias in the zinc-diffused diodes and for most of the bias range in the beryllium-diffused diodes, the dominant forward current was due to thermal recombination in the space-charge region via deep traps. The reverse current in the pre-avalanche breakdown region for all diodes appeared to be dominated by internal field emission, or Zener tunneling.