EVOLUTION OF DEEP LEVELS AND INTERNAL PHOTOEMISSION WITH ANNEALING TEMPERATURE AT ZNSE GAAS INTERFACES/

We have measured charge states deep within the ZnSe band gap and local ized near the ZnSe/GaAs interface as a function of annealing temperatu re by means of photoluminescence spectroscopy, as well as cathodolumin escence from the cross section of a ZnSSe/GaAs heterostructure with a scanning electron microscope. Annealing produces new emissions at 1.9 eV and 2.25 eV which increase with annealing temperature and which var y with different growth conditions. Cathodoluminescence spectra show t wo similar features which originate within ZnSe and whose relative emi ssion intensities vary with depth. Since the 2.25 eV feature appears o nly under Zn-rich growth conditions, these results indicate a role of both interface diffusion and crystal growth in the formation of this d efect. We observe a proportional increase of the 1.9 eV and 0.9 eV pea k intensities with annealing, indicating their complementary nature wi th respect to a common deep level. Finally, a detailed analysis of the relative intensities of ZnSe and GaAs features due to internal photoe mission across the heterointerface suggests that the heterojunction ba nd offset changes with formation of these new deep levels. All these r esults emphasize that multiple deep levels form near the buried interf ace with annealing which can dominate the heterojunction electronic pr operties. (C) 1996 American Vacuum Society.