CATHODOLUMINESCENCE QUANTUM-WELL STUDIES

The advent of quantum well structures has given rise to new physics and new technology. Quantum well propertiees are determined by interfaces between chemically distinct, heterostructural compounds. The study of these interfaces is of vital importance to the progress of this field, and many studies using a variety of techniques have been made. The scanning cathodoluminescence microscope has made major contributions to the understanding of interfaces in quantum well devices but has previously been limited to a spatial resolution of almost-equal-to 1-mu-m. We have achieved 60 nm spatial resolution in this mode by: 1) using a small probe generated by an intense field emission source; 2) using a 1 almost-equal-to 2 kV beam to inject both near the surface and with minimal lateral scattering (10 almost-equal-to 30 nm); and 3) by detecting photons from pre-diffusion radiative recombination events. Carriers living longer than almost-equal-to 10 ps recombine non-radiatively at the surface; the surface acts as a picosecond "shutter". We force surface recombination to dominate the lifetime by injecting very close to the surface.