COEXISTENCE OF 2H AND 4H POLYTYPES IN ZN1-XMGXSE OBSERVED BY PHOTOLUMINESCENCE AND CATHODOLUMINESCENCE

Zn1-xMgxSe mixed crystals grown from the melt, with a value of x close to 0.19 have been characterized by photoluminescence (PL) and cathodo luminescence (CL) methods. We have observed two emission lines at 3.02 5 eV and at 3.075 eV at 40 K in PL as well as in CL spectra instead of the usually seen only one exciton line. Applying spectrally resolved cathodoluminescence enabled us to interpret the two near-band-edge emi ssion lines observed in PL and CL spectra as due to radiative recombin ation of free excitons in 4H and 2H polytype structures coexisting in the same sample. These results also demonstrate the analytical capabil ities of the cathodoluminescence. (C) 1998 Elsevier Science Ltd. All r ights reserved.