Transmission electron microscopy and cathodoluminescence of tensile-strained GaxIn1-xP/InP heterostructures .2. On the origin of luminescence heterogeneities in tensile stress relaxed GaxIn1-xP/InP heterostructures

We have determined the origin of the spatial luminescence fluctuations observed between the dark line defects present in tensile strained GaxIn1-xP/In1-xP/n(+)-InP heterostructures (Part I [F. Cleton et al. J. Appl. Phys. 80, 827 (1996)]). For that purpose, we have undertaken semi-quantitative and spectroscopic cathodoluminescence (CL) measurements on various specimens in areas exhibiting CL contrasts which could be as large as 80%. The analysis of the variation of the CL polychromatic signal with electron beam energy allowed us to get information on the diffusion-recombination (DR) parameters of the areas under study. From the correlation between the local relaxation level of these areas and their DR parameters, we can conclude that the variation of the misfit dislocations density at the GaxIn1-xP/InP interface is at the origin of the luminescence heterogeneities. We also demonstrate that recycling, by the GaxIn1-xP epilayer, of the photons originating from the heavily doped InP substrate, enhances the CL contrast between areas exhibiting different relaxation levels. (C) 1996 American Institute of Physics.