EXCITONS TRAPPED ON SELF-ORGANIZED CDTE ISLANDS IN WIDE ZNTE QUANTUM-WELLS

Optical spectroscopy has been performed on samples grown by molecular beam epitaxy on the (001) surface of ZnTe substrates, all basically co nsisting of similar to 38 nm wide ZnTe - (Zn,Mg)Te quantum wells, in w hich five separate monolayers containing cadmium atoms have been inser ted, equally spaced by 20 monolayers of ZnTe, along the growth axis. T wo samples are presented, containing five half CdTe monolayers deposit ed, respectively, by molecular beam epitaxy (yielding wide flat island s of CdTe separated by wide ZnTe areas), and by atomic layer epitaxy ( yielding a quasi-homogeneous planar distribution of cadmium atoms). Th e inserts introduce two spectral features corresponding to heavy-and l ight-hole excitons trapped on CdTe which acts as a potential well for electrons and both types of holes. The ground exciton yields a very ef ficient photoluminescence, a few meV below the excitonic gag of ZnTe. The fine structure of photoluminescence spectra reveals the presence o f a low-energy feature assigned to a X- excitonic complex. The tempera ture dependence of the emission intensity is also studied. (C) 1998 El sevier Science B.V. All rights reserved.