PHOTOSTIMULATED EMISSION OF GAN LAYERS AND DEVICES

Photostimulated emission (PSE) of epitaxial GaN layers is readily obta ined at photoexcitation densities of order MW cm(-2) at temperatures u p to room temperature. We report surprising spectral differences betwe en PSE obtained using surface and edge emission geometries for a parti cular sample. While the peak energy of PSE from the surface of this sa mple is downshifted from the GaN band edge by only a small amount, the photon energy of the edge-emitted light is reduced by similar to 100 meV. Exactly the same downshift is observed in the edge emission spect rum of a commercial Nichia light emitting diode. The origin of the ano malous PSE peaks revealed ill these measurements is discussed with ref erence to recent literature. (C) 1997 Elsevier Science S.A.