Pulsed laser induced effects on the HgCdTe surface

Abstract

Laser annealing of mercury cadmium telluride (MCT) is interesting from both physical and practical perspectives. We have investigated the behavior of nominal Hg1−xCdxTe(x=0.2) wafers under pulsed laser irradiation and analyzed the role of some of the laser beam parameters. Rutherford backscattering spectroscopy (RBS), auger sputter depth profiling (SDP), and scanning electron microscopy (SEM) have been used to achieve a general picture of the process and to characterize the compositional, morphological, and order–disorder changes produced by the laser irradiation. We report the first depth profiles of laser treated MCT by both RBS and Auger SDP techniques. Significant differences are found when compared with results for other annealing methods. A Te-rich layer is observed at the surface. The Hg deficient region is found a few tens of monolayers below the top of the surface with the maximum depletion at 18–30 nm. At this depth, small increases of Hg concentration are detected in the surrounding nonirradiated areas. Thermal and compositional changes are discussed taking into account that laser irradiation produces the melting of surface and near-surface regions and a consequent liquid phase epitaxial regrowth.