PHOTO-ASSISTED MOLECULAR-BEAM EPITAXY OF CDTE-CDMNTE HETEROSTRUCTURES

Photo-assisted molecular beam epitaxy (PAMBE) is a new growth technique that has been developed to enhance the substitutional doping of II-VI compound semiconductors. To investigate the underlying mechanism of the PAMBE growth process, detailed reflection high energy electron diffraction studies on the reconstruction of CdTe(100) substrates has been completed. These studies have shown that one of the major effects of the PAMBE growth process is to enhance the cadmium concentration at the growth surface. As an application of the PAMBE growth technique, high quality CdMnTe-CdTe heterostructures have been grown. The successful MBE growth of CdMnTe-CdTe heterostructures and superlattices has demonstrated the feasibility of growing layered structures incorporating dilute magnetic semiconductor (DMS) materials. The reflectance, photoluminescence and excitation photoluminescence of CdTe-CdMnTe single- and multiple-quantum-well structures with well widths in the range 30-45 angstrom have been investigated at low temperatures. These show bright, narrow (less than 1 mev) luminescence features. Recently we have observed for the first time free magnetic polarons in DMS quantum wells. Free- and bound-magnetic-polaron energies were determined by the suppression of polaron formation with increasing temperature and in external magnetic fields.