CAN FRACTAL-LIKE SPECTRA BE EXPERIMENTALLY OBSERVED IN APERIODIC SUPERLATTICES

We numerically investigate the effects of inhomogeneities in the energ y spectrum of aperiodic semiconductor superlattices, focusing our atte ntion on Thue-Morse and Fibonacci sequences. In the absence of disorde r, the corresponding electronic spectra are self-similar. The presence of a certain degree of randomness, due to imperfections occurring dur ing the growth processes, gives rise to a progressive loss of quantum coherence, smearing out the finer details of the energy spectra predic ted for perfect aperiodic superlattices and spurring the onset of elec tron localization. However, depending on the degree of disorder introd uced, a critical size for the system exists, below which peculiar tran sport properties, related to the pre-fractal nature of the energy spec trum, may be measured.