Alloy-scattering and strain-fluctuation-scattering contributions to the low-temperature electron mobility in ternary quantum wells and heterostructures

We present theory and data for the low-temperature electron mobility in ternary quantum wells (QW’s). In our model the electrons are scattered from spatially fluctuating strain-induced potentials and alloy potentials arising from alloy disorder both in lattice-matched and strained QW’s. We find that the mobility does not depend sensitively on the amount of the average strain in the ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum well but on the strain fluctuation. Lower mobilities observed in strained quantum wells are explained in terms of possible clustering effects which may be more severe in strained systems: The theoretical results agree with our data from strained ${\mathrm{In}}_{0.2}$${\mathrm{Ga}}_{0.8}$As/GaAs QW’s for a clustered In-atom distribution. On the other hand, the recent data from lattice-matched ${\mathrm{In}}_{0.53}$${\mathrm{Ga}}_{0.47}$As/${\mathrm{In}}_{0.52}$${\mathrm{Al}}_{0.48}$As heterostructures are reasonably explained for a microscopically random In-atom distribution without using the clustering assumption.