LUMINESCENCE CAUSED BY EXTENDED LATTICE-DEFECTS IN EPITAXIALLY GROWN ZNTE LAYERS

Two strong emission bands (Y1 and Y2), 210 and 250 meV lower than E(ga p) of ZnTe, have been studied in heteroepitaxially grown ZnTe layers. The phonon coupling and the thermalization energy of these emissions a re unusually small, similar to those of the Y band in ZnSe and CdTe la yers. The Y luminescence in ZnTe is emitted above all near the ZnTe/Ga As interface which contains a high density of lattice defects (mainly misfit dislocations). An increasing concentration of point defects lea ds to a strong decrease of the Y emission. The observation of this lum inescence in ZnTe bulk material or in homoepitaxially grown ZnTe is no t possible because of a strong dependence of the intensity on the defe ct concentration and the dislocation density. Both bands are excited o nly by laser light resonant to or higher than the free exciton energy. The strain dependent energy shift behaves similar to that of bound ex citons. The intensity of the Y bands observed at liquid helium tempera ture decreases under strong laser excitation. A recovery effect of bot h lines is observed when the sample is heated to liquid nitrogen or ro om temperature.