Analysis of native oxides grown on single-crystal CdTe and MgCdTe

Abstract

Over the course of CdTe photovoltaics development, many refinements to the device stack have been made. One area of current interest is the back contact interface, where surface passivation is critical to prevent recombination at the interface. One candidate material for achieving strong passivation is TeO2. Using scanning transmission electron microscopy, we investigate native oxide formations on CdTe and MgxCd1−xTe substrates to better understand the oxides' chemical composition and the interface they form with the material they are grown on. We find that substoichiometric TeOx forms as a native oxide on CdTe, and on MgxCd1−xTe, we found a MgO native oxide. Some TeOx appeared atop the MgO layer, though it was not consistently present. The native oxides had preferential interface terminations, with Cd terminations at the CdTe/TeOx interface and Te terminations at the MgxCd1−xTe/MgO interface.