The effect of surface recombination on current in AlxGa1−xAs heterojunctions

Abstract

We show that the 2kT current in double‐heterostructure Al_xGa_1−xAs p‐n junctions is primarily due to surface recombination at the junction perimeter. The rate of surface recombination is evaluated by means of two luminescence experiments. Both experiments provide evidence that the rate of surface recombination increases with bias as exp(eV/2kT) and has the correct magnitude to account for the measured I‐V curves. It is shown theoretically that recombination at a depleted surface is proportional to exp(eV/2kT) at high bias. The 2kT behavior is a consequence of the nearly constant ratio of electron and hole densities at the surface. The nearly constant ratio is needed to maintain equality of surface and surface depletion layer charge. p‐n junction perimeters of cleaved, etched, and proton‐bombarded interfaces are evaluated and found to have similar rates of nonradiative recombination with the rate of surface recombination given by R=s₀(np)^1/2, where s₀ is approximately 4×10⁵ cm/sec.