Symmetric and asymmetric fractal diffusion of electron-hole plasmas in semiconductor quantum wells

The diffusion of photogenerated electron-hole plasmas in intrinsic InP/InGa As/InP single quantum wells was investigated by measurements of the photolu minescence intensity profile around the illuminated area. Two kinds of hete rostructures were investigated, one grown on InP substrate with the growth face orthogonal to the [001] direction, and the other grown on InP substrat e two degrees off that orientation. The data show that the particles presen t a fractal diffusion described by the Levy distribution with the exponent parameter alpha = 1.3. In the tilted heterostructure, the diffusion is asym metric and the particles density obeys a generalized Levy distribution rece ntly predicted by Chaves [Phys. Lett. A 239 (1998) 13]. (C) 2000 published by Elsevier Science B.V. All rights reserved.