Plan-view transmission electron microscopy and cathodoluminescence images were obtained from the same sample, at exactly the same location, of n-type material which had been grown onto sapphire substrates by means of metal-organic chemical vapor deposition. It was found that there was a clear one-to-one correspondence between the dark spots which were observed in cathodoluminescence images and the dislocations in transmission electron microscopy foils. This indicated that the dislocations were non-radiative recombination centers. The hole diffusion length in n-type material was estimated to be about 50nm by comparing the diameters of the dark spots in thick samples which were used for cathodoluminescence studies with samples which were thinned for transmission electron microscopic observation. The efficiency of light emission was high when the minority carrier diffusion length was shorter than the dislocation spacing.

T.Sugahara, H.Sato, M.Hao, Y.Naoi, S.Kurai, S.Tottori, K.Yamashita, K.Nishino, L.T.Romano, S.Sakai: Japanese Journal of Applied Physics - 2, 1998, 37[4A], L398-400