Optical study of the indium accumulation in strained quantum wells

Indium surface segregation depends drastically on the elaboration condition. It induces, for low energy transitions, a blue-shift. But in some samples the opposite phenomon has been observed. Experimental photoluminescence (PL) line energies are below those calculated by the square model potential of the quantum well. This phenomenon can be attributed to the indium atoms accumulation on the last layer of the nominal quantum well. To identify the PLE transitions, we have modified the model of indium surface segregation proposed by Nagle et al. by introducing an adjustable parameter br, which is associated to the quantity of indium atoms accumulated. For large nominal well width and/or indium concentration, this induces the existence of a second photoluminescence line (shoulder) in the low energy side of the main one. (C) 1998 Elsevier Science B.V. All rights reserved.