Cathodoluminescence spectroscopy of deep defect levels at the ZnSe/GaAs interface with a composition-control interface layer

In this work we investigate ZnSe/GaAs heterostructures with an additional 2 nm controlled interfacial layer (CIL) of Se- or Zn-rich composition to mod ify the band offset. The samples are analyzed as a function of annealing te mperature by cathodoluminescence spectroscopy. The as-prepared samples show defect luminescence at similar to 0.9 eV, With staged annealing at increas ing temperatures, both the Zn-rich as well as the Se-rich interfacial layer exhibits luminescence at similar to 1.9 eV, indicative of defect formation with an onset temperature of similar to 400 degrees C, Excitation-dependen t spectroscopy provides evidence for defect formation near the interface, w hich extends into the ZnSe epilayer at higher temperatures. Compared to ear lier work, where the threshold temperature for defect formation in bulk sam ples fabricated under Se-rich growth conditions occurs at temperatures as l ow as 325 degrees C, the resistance to defect formation has now been improv ed to that of stoichiometric ZnSe, These results demonstrate that epitaxial ly grown CILs provide a means to alter ZnSe/GaAs band offsets without degra ding the heterojunction's resistance to defect formation at elevated temper atures.