INCORPORATION OF IODINE INTO CDTE BY DIFFUSION

Initial studies on the diffusion of iodine into CdTe are described. Diffusion anneals were carried out at selected temperatures in the range between 20 and 270-degrees-C in evacuated silica ampoules using a diffusion source of either elemental iodine or CdI2, both under saturated vapour pressure conditions. The concentration profiles were measured using either a radiotracer sectioning technique or secondary ion mass spectrometry (SIMS). The profiles were found to be composed of four parts to which a computer package consisting of the sum of four complementary error functions (erfc) gave satisfactory fits to the data. The fastest diffusing component gave values of the diffusivity, which agreed with previously published data. Proposals explaining how this type of diffusion may occur are given, but the results indicate that iodine diffused into CdTe from the vapour is not suitable as a long term stable dopant in devices where sharp junctions are required.