ROLE OF LOCALIZED AND EXTENDED ELECTRONIC STATES IN INGAN GAN QUANTUM-WELLS UNDER HIGH INJECTION, INFERRED FROM NEAR-FIELD OPTICAL MICROSCOPY/

We report on spatially resolved optical measurements of high-quality I nGaN/GaN multiple quantum wells under conditions of direct high optica l injection (> 10(19) cm(-3)) using near-field optical microscopy in t he collection mode. The spectral dependence of the spatial distributio n of the photoluminescence indicates that the range of In-composition fluctuations reaches the 100-nm lateral scale. The spectra are depende nt on the carrier injection level and reveal significant state filling effect. We sketch tentative conclusions about the In-cluster size dis tribution in terms of contributions to the radiative processes that in volve localized and extended states, respectively, in the regime of el ectron-hole (e-h) pair densities at which present diode lasers operate . (C) 1998 American Institute of Physics.