Where the metal-semiconductor junction emits light

Abstract

Determination of the spatial distribution of excited luminescence centers in a junction is crucial for testing any model of high-field electroluminescence. A simple method of a quasi-direct profiling of emission in a metal-semiconductor (MS) junction is introduced. The method is based upon the effect of Auger quencing of a localized-centre luminescence by either free or bound electrons. Since the efficiency of this effect is controlled by the Fermi-level position the kinetics of electroluminescence (EL) is governed by the motion of a depletion layer edge following a rapid change of a junction bias. Simultaneous measurement of the EL kinetics and width of a depletion layer allows for a determination of a spatial excitation profile. The method is illustrated by the experiment performed on EL-MS diodes made on CdF 2:Mn, Y crystals. It is shown that EL is generated only in a region close to the depletion layer edge, thus proving a spatial separation of the carrier acceleration and the collision excitation processes in high-field electroluminescence.