Disorder induced coherence-incoherence crossover in random GaAs/AlGaAs superlattices

The coherence of electrons was studied in intentionally disordered GaAs/AlGaAs superlattices as a function of the vertical interlayer coupling. Depending on the relation of the disorder energy and the Fermi energy the coherent and incoherent diffusive transport regimes were distinguished. New features of weakly coupled layered electron systems such as the vertical coupling energy and the in-plane phase-breaking time were observed by magnetoresistance measurements in the coherent and incoherent regimes respectively. Both of them were found to decrease with increasing disorder strength. This demonstrates the disorder induced break-down of the interlayer coherence of quasi-particles which drastically affected their intralayer coherence.