PROCESSING AND CHARACTERIZATION OF LARGE-GRAIN THIN-FILM CDTE

Basic material studies addressing the growth and processing of CdTe ha ve resulted in dense, defect-free as-grown CdTe films on 7059 glass wi th initial grain sizes of almost-equal-to0.2 mum. Innovations in postd eposition processing (no CdCl2) have resulted in films with >50 mum gr ain sizes. Scanning electron microscopy analyses confirm film density while concurrent cathodluminescence reveals a change in the recombinat ion efficiency. Transmission electron microscopy analyses reveal that films grown below 300-degrees-C are defect-free, while films grown abo ve 300-degrees-C contain defects. Photoluminescence lifetime measureme nts reveal a fivefold increase in lifetime following posdeposition pro cessing of these films. These results were correlated with x-ray photo emission measurements of the Te 4d, Cd, 4d, and valence band. This ind icates that grain boundaries are the main factor limiting lifetimes. B ased on these results, we have developed an understanding of the effec ts of oxygen and grain boundary oxides on postdeposition processing an d enhanced grain growth.