Effect of interface recombination at AlxGa1−xAs p–n junction perimeters on photoluminescence and current

The interfaces forming the perimeters of AlxGa1−xAs p–n junctions, such as cleaved surfaces or etched surfaces are regions of intense nonradiative recombination. Almost all of the p–n junction 2kT current is due to recombination at these nonradiative perimeters. When an uncontacted sample is studied in photoluminescence, these interfaces produce broad nonradiative regions known as large dark spots. The rate of interface recombination can be quantitatively evaluated from measurement of either the 2kT current or the large dark spot line shape. The 2kT current is usually explained in terms of the Sah, Noyce, and Shockley model of p–n depletion layer recombination. We develop an alternative model in which we show that recombination at a depleted surface will have 2kT charater. The rate of surface recombination is R=s0(np)1/2=s0ni exp(eV/2kT) where s0?4×105 cm s−1 for x=0.08 active layers with etched surfaces. This form of the recombination rate follows naturally from the requirement that the interface remain neutral.