SURFACE AND PERIMETER RECOMBINATION IN GAAS DIODES - AN EXPERIMENTAL AND THEORETICAL INVESTIGATION

Surface and perimeter recombination in GaAs heteroface diodes was studied experimentally and by two-dimensional numerical simulation including Fermi-level pinning. Perimeter and bulk current components were experimentally extracted, and the numerical model was used to study the origin of perimeter current in these devices. Under moderate bias, perimeter recombination occurs primarily within the junction depletion region, but as the bias is increased the perimeter outside of the junction depletion region becomes increasingly important. A bias dependence of the perimeter current ideality factor was observed both experimentally and theoretically and was attributed to the perimeter recombination of injected carriers diffusing to the perimeter from the bulk regions. Fermi-level pinning was shown to increase the effective surface-recombination velocity, but conduction along the surface channel plays little role in these devices. The results demonstrate that a simple numerical treatment of Fermi-level pinning and surface recombination can accurately account for surface and perimeter recombination in GaAs homojunction diodes.