CDSE ZNSE QUANTUM STRUCTURES GROWN BY MIGRATION-ENHANCED EPITAXY - STRUCTURAL AND OPTICAL INVESTIGATIONS/

Migration enhanced epitaxy has been applied to induce the change from two-dimensional growth to formation of self-assembling islands in the growth of CdSe on ZnSe. Transmission electron microscopy images from s amples with a ZnSe caplayer show a transition from a flat quantum well to an interrupted layer with pronounced thickness fluctuations when t he CdSe exceeds its critical thickness. These results are confirmed by high resolution x-ray diffraction measurements, as only for the forme r sample the 004 rocking curve can be simulated assuming a flat quantu m well with abrupt interfaces. Compared to bulk CdSe, the photolumines cence peak is blueshifted by about 0.5 eV. PL excitation experiments i ndicate that the interrupted layer consists of CdSe islands embedded i n Zn1-xCdxSe with a composition gradient. Atomic force microscopy imag es of uncapped samples show spherical islands with a height of 20 nm a nd a diameter-to-height ratio of 4:1. (C) 1997 American Institute of P hysics.