Two strong emission bands (Y1, Y2), which were 0.21 and 0.25eV lower than Egap, were studied in hetero-epitaxially grown layers. The phonon coupling and thermalization energy of these emissions were unusually small, and were similar to those of the Y band in ZnSe and CdTe layers. The Y luminescence in ZnTe was emitted mainly near to the ZnTe/GaAs interface which contained a high density of lattice defects (especially misfit dislocations). An increasing concentration of point defects led to a marked decrease in Y emission. Observation of this luminescence in bulk ZnTe or in homo-epitaxially grown ZnTe was not possible, because of a strong dependence of the intensity upon the defect concentration and the dislocation density. Both bands were excited only by laser light which was resonant to, or higher than, the free exciton energy. The strain-dependent energy shift behaved similarly to that of bound excitons. The intensity of the Y bands which were observed at liquid He temperatures decreased under strong laser excitation. Recovery of both lines was observed when the sample was heated to liquid N or ambient temperatures.

K.Wolf, A.Naumov, T.Reisinger, M.Kastner, H.Stanzl, W.Kuhn, W.Gebhardt: Journal of Crystal Growth, 1994, 135[1,2], 113-22