Laser Scanning Confocal Microscopy for Defect Analysis in CdTe Thin Films

Cadmium telluride (CdTe) is a key semiconductor for thin-film solar cells, but device efficiency is hindered by structural defects and non-radiative recombination. In this work, we grow CdTe doped with Arsenic by molecular beam epitaxy (MBE) and use infrared (IR) laser scanning confocal microscopy (LSCM) to non-invasively characterize defects. The confocal microscope enabled visualization of extended defects, while MBE provides precise control of As doping CdTe. We studied two CdTe thin films, (S1 and S2), doped with arsenic, and one bare CdTe substrate (S). Both S1 and S2 were grown under the exact same growth conditions other than the operating temperature of the CdAs cell for the As doping. The dominant defects observed were twin defects for both samples. Specifically, at 60x magnification, S2 had a defect density of 0.169 defects per μm² and S1 had no visible defects at this scale. This study highlights the importance of both defects' characterization and controlled growth techniques in advancing performance and understanding of next generation telluride-based materials.