HETEROEPITAXIAL GROWTH OF N-TYPE CDSE ON GAAS(001) BY PULSED-LASER DEPOSITION - STUDIES OF FILM-SUBSTRATE INTERDIFFUSION AND INDIUM DIFFUSION

Epitaxial CdSe films were grown on (001)-oriented and 2 degrees-miscut GaAs wafers at platen temperatures (T-p) of 250-425 degrees C by ArF (193 nm) pulsed excimer laser ablation of a stoichiometric CdSe target in vacuum and low-pressure Ar gas. The substrates were bonded to the platen with indium solder or silver paint. Auger electron spectroscopy (AES) combined with ion sputtering and energy dispersive X-ray fluore scent spectroscopy were employed to investigate him-substrate interdif fusion, the presence of indium or silver in the films, and CdSe film s toichiometry, all as functions of the him-growth conditions. Extensive interdiffusion took place at the film-substrate interface for CdSe fi lms grown at T-p greater than or equal to 355 degrees C but was greatl y reduced at T-p = 250 degrees C. Tilting the substrate to be approxim ately parallel to the ablation plume as well as increasing the ambient gas pressure also reduced film-substrate interdiffusion. Indium was f ound in films deposited at T-p greater than or equal to 355 degrees C while no In was detected in films deposited at T-p = 250 degrees C. AE S depth profiling showed that the In concentration was highest at the CdSe Olm surface and that the Cd concentration varied inversely with t he In concentration. At higher In concentrations the Se concentration also varied inversely with the In concentration in the near-surface re gion, implying that In clusters or interstitials may exist in addition to substitutional indium. In the absence of indium diffusion the CdSe films were nearly stoichiometric. No silver was found in any film. (C ) 1998 Elsevier Science B.V. All rights reserved.