Interdiffusion study of HgTe–HgCdTe superlattice. I. Low‐temperature Auger sputter depth profiling Available to Purchase

It has been suggested that some discrepancies between theoretical and experimentally measured band‐gap values may arise from interdiffusion which occurs during superlattice growth. Previously, no analytical technique had been sufficiently developed to provide compositional depth profiling with high enough depth resolution to characterize superlattice structures. We report the development of Auger sputter depth profiling (SDP) of HgCdTe superlattices at cryogenic temperatures and the subsequent investigation of superlattice interdiffusion using this technique. First, we studied Hg desorption, sputter rates, and preferential sputtering on molecular‐beam epitaxy (MBE) and liquid phase epitaxy grown HgTe and CdTe standards as well as HgCdTe samples at room temperature and at −126 °C to understand the effect of electron and ion beams on these materials and subsequent analysis. Next, we were successful in obtaining a high‐resolution Auger SDP of an MBE grown ‘‘square‐wave’’ HgTe–Hg_0.15Cd_0.85Te (52 Å/80 Å) and a laser MBE grown ‘‘sawtooth’’ superlattice at −126 °C by optimizing beam parameters. We show that these optimized analysis parameters have a minimal effect on the structure of the superlattice, thereby enabling quantitative measurements in addition to accurate structural analysis. Finally, we report an interdiffusion study on a 200‐Å period laser MBE grown sawtooth HgTe–CdTe superlattice (as‐grown versus annealed at 205 °C). The asymmetry due to the sawtooth structure in the unannealed superlattice was clearly visible in the Auger SDP. A change in average composition as well as a 5% variation in layer thicknesses was observed. These data imply that we were able to identify thickness variations as small as 10 Å. Significant structural changes were apparent in the Auger SDP of the annealed sample. This is the first investigation using low‐temperature Auger SDP as a tool for precisely analyzing HgCdTe superlattice structures.