Effects of spontaneous and piezoelectric polarizations on carrier confinement at the Zn 0.88 Mn 0.12 O/ZnO interface

For Zn1-xMnx O/ZnO heterostructures pseudomorphically grown on ZnO (000) single-crystal substrates, spontaneous and piezoelectric polarization-induced sheet charges were investigated. The sheet carrier concentration of a Zn0.88Mn0.12O/ZnO heterostructure with a 10-nm-thick ZnMnO spacer layer was determined to be 5.6×1012 cm–2 by Hall measurement. For x = 0.12, the number of free electrons induced by spontaneous and piezoelectric polarizations was calculated to be 1.8×1012 cm–2, which is less than the experimental value. This discrepancy can be explained by considering an additional electric field generated by the ZnMnO/ZnO conduction band offset and ZnMnO spacer layer. Therefore, for ZnMnO/ZnO heterostructures, the effect of electric field should also be considered together with spontaneous and piezoelectric polarizations in carrier confinement. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)