Stability and band offsets between c-plane ZnO semiconductor and LaAlO3 gate dielectric

Abstract

Wurtzite-perovskite heterostructures composed of a high dielectric constant oxide and a wide bandgap semiconductor envision promising applications in field-effect transistors. In the present paper, the structural and electronic properties of LaAlO3/ZnO heterojunctions are investigated by first-principles calculations. We study the initial adsorption of La, Al, and oxygen atoms on ZnO (0001) and (0001¯) surfaces and find that La atoms may occupy interstitial sites during the growth of stoichiometric ZnO (0001). The band gap of the stoichiometric ZnO (0001) surface is smaller than that of the stoichiometric ZnO (0001¯) surface. The surface formation energy indicates that La or Al atoms may substitute Zn atoms at the nonstoichiometric ZnO (0001) surface. The atomic charges, electronic density of states, and band offsets are analyzed for the optimized LaAlO3/ZnO heterojunctions. There is a band gap for the LaAlO3/ZnO (0001¯) heterostructures, and the largest variation in charge occurs at the surface or interface. Our results suggest that the Al-terminated LaAlO3/ZnO (0001¯) interfaces are suitable for the design of metal oxide semiconductor devices because the valence and conduction band offsets are both larger than 1 eV and the interface does not produce any in-gap states.