  In this paper, the reported experimental data in [Sci. Rep., 2012, 2, 533]
related to electrical transport properties in bulk ZnO, ZnMgO/ZnO, and
ZnMgO/ZnO/ZnMgO single and double heterostructures were analyzed quantitatively
and the most important scattering parameters for controlling electron
concentration and electron mobility were obtained. Treatment of intrinsic
mechanisms included polar-optical phonon scattering, piezoelectric scattering
and acoustic deformation potential scattering. For extrinsic mechanisms,
ionized impurity, dislocation scattering, and strain-induced fields were
included. For bulk ZnO, the reported experimental data were corrected for
removing the effects of a degenerate layer at the ZnO/sapphire interface via a
two layer Hall effect model. Also, donor density, acceptor density and donor
activation energy were determined via the charge balance equation. This sample
exhibited hopping conduction below 50K and dislocation scattering closely
controlled electron mobility closely. The obtained results indicated that the
enhancement of electron mobility in double sample, compared with the single
one, can be attributed to the reduction of dislocation density, two dimensional
impurity density in the potential well due to background impurities, and/or
interface charge and strain-induced fields, which can be related to better
electron confinement in the channel and enhancement in the sheet carrier
concentration of 2DEG in this sample.
