Self-organization of packing defects and Anderson localization in A3B6-type layered crystals

It is shown that the weakness of interlayered bounds in A(3)B(6)-type layered crystals leads to layer shift and the self-organization of packing defects, which results in a localization of electron states along the c-axis. The localization of electron states lead to the observation of hopping conductivity with variable range hopping and an Anderson transition at high optical excitation level when the majority carrier quasi-Fermi level crosses the mobility edge. The values of localization width, DeltaE(o), in different InSe and GaSe crystals are changing from 10 to 100 meV. Especially, in crystals doped by non-isoelectronic impurity atoms, low values of DeltaE(o) are obtained. We assume that this fact is related to structure ordering of doped crystals. The correlation between conductivity anisotropy and localization width was also found. (C) 2002 Published by Elsevier Science B.V..