LOW-ENERGY CATHODOLUMINESCENCE SPECTROSCOPY STUDIES OF III-V SUPERLATTICE INTERDIFFUSION - OPTICAL-EMISSION PROPERTIES OF DIFFUSION ASSOCIATED DEFECTS

We report a direct optical observation of process-specific diffusion-related deep levels associated with interdiffusion in AlGaAs/GaAs superlattice structures. We have used low-energy cathodoluminescence spectroscopy (CLS) to investigate the formation and evolution of deep levels for intrinsic, under As overpressure, and Si induced layer intermixing. The spatial distribution of these deep levels strongly correlates with the extent of superlattice intermixing, as measured by secondary ion mass spectroscopy (SIMS) and photoluminescence spectroscopy (PLS). The measured cathodoluminescence emission energies and intensities reveal the important role of impurities in the mechanism of interdiffusion at III-V semiconductor superlattices. In particular, our experimental results strongly suggest that the larger interdiffusion rate of the Si induced layer intermixing process is related to the formation of a deep level associated with an optical emission at 1.3 eV. These results indicate the potential of the low-energy cathodoluminescence technique for studying deep level formation and deep level inhomogeneities in semiconductor structures.