Role of heteroepitaxial misfit strains on the band offsets of Zn12xBexO/ZnO quantum wells: A first-principles analysis

There is a growing interest in Zn1 xBexO (ZBO)/ZnO heterostructures and quantum wells since the band gap energy of ZBO solid solutions can be tuned over a very large range (3.37–10.6 eV) as a function of the Be composition. Due to its extremely large exciton binding energy (263 meV for Zn0.8Be0.2O/ZnO), ZBO/ZnO has been utilized in ultraviolet light emission diodes and lasers, and may find applications as active elements of various other electronic and optoelectronic devices. In this study, we report the results of an ab initio study on valence and conduction band offsets (DEC and DEV) of strain-free and epitaxial ZBO/ZnO heterostructures. These offsets determine the degree of the localization of charges at the interfaces of semiconductor multilayers and thus their electronic/ optoelectronic properties. We show that while DEV of strain-free ZBO/ZnO varies almost linearly from 0 eV to 1.29 eV as Be composition increases from 0 to 1, there is a large nonlinear increase in DEC from 0 eV for x1⁄4 0 to 5.94 eV for x1⁄4 1 with a bowing parameter of 5.11 eV. To understand the role of misfit strains, we analyze epitaxial c-plane and m-plane Zn0.75Be0.25O/ZnO heterostructures. Due to the differences in the atomic displacements for the two growth orientations, DEC and DEV of c-plane Zn0.75Be0.25O/ZnO are significantly larger than those of m-plane Zn0.75Be0.25O/ZnO heterostructures. VC 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729079]