TRANSIENT PHOTOINDUCED ABSORPTION IN (ALXGA1-X)(0.5)IN0.5P FRACTAL QUANTUM-WELL HETEROSTRUCTURES

Picosecond photoinduced absorption measurements have been performed on four different (AlxGa1-x)(0.5)In0.5P fractal quantum well heterostruc tures. The results of these measurements reveal that, at early times f ollowing pulsed excitation, the carriers remain near the surface layer in which they were photogenerated, and populate the higher lying bran ches of the V-shaped fractal structure. With increasing time, the carr ier population relaxes toward the lowest energy, central wall. The rat e at which the relaxation occurs is governed by the characteristic lay er of widths of the fractal structure.