Valence-band offset of epitaxial ZnO/MgO (111) heterojunction determined by x-ray photoelectron spectroscopy

The valence-band offset of ZnO/MgO (111) heterojunction has been directly measured by x-ray photoelectron spectroscopy. Excluding the strain effect, the valence-band offset is determined to be 0.87 +/- 0.20 eV, and the conduction-band offset Delta E-C is deduced to be -3.59 +/- 0.20 eV, indicating that ZnO/MgO heterojunction has a type-I band alignment. The conduction-band and valence-band offset of MgO/ZnO is used to interpret the origination of p-type conduction in undoped MgxZn1-xO alloy and deeper acceptor level in undoped and N-doped p-type MgxZn1-xO alloy than in ZnO. (c) 2008 American Institute of Physics.