PHOTOASSISTED MOLECULAR-BEAM EPITAXY OF WIDE GAP II-VI HETEROSTRUCTURES

Photoassisted molecular beam epitaxy (PAMBE) is a new growth technique that has been developed to enhance the substitutional doping of II-VI compound semiconductors. During the process the substrate is illuminated during the growth sequence. In the present work a modified Riber MBE 2300 system was employed. A modification to the commercial system was made such that the substrate could be illuminated with an argon-ion laser during the deposition. The effect of illumination power density on the PAMBE growth of undoped CdTe has been studied in detail. With increasing power density we see the appearance of a new, very narrow (0.18 meV) and very intense luminescence feature. Polarization studies have been recently completed showing that this line is strongly linearly polarized along one of the crystallographic axis. We have observed for the first time strongly linearly polarized luminescence for undoped (100)CdTe epitaxial layers grown by photoassisted molecular beam epitaxy. The observation of this linear polarization leads us to postulate that the A-line and B-line observed in PAMBE grown CdTe are associated with vacancy-donor complexes that are preferentially oriented during the layer by layer growth process. The effect of illumination power density on the mobility and carrier concentration in undoped and lightly doped CdTe epilayers has been studied in detail. At low power densities we see an increase in both the mobility and carrier concentration. © 1989.