Interface structure and polarity of GaN/ZnO heterostructure

Abstract

Gallium nitride (GaN) films were grown with and without lattice-matched (In,Ga)N buffer layers on the c(+) and c(-) faces of ZnO single-crystal substrates using molecular beam epitaxy, and their interface structures, including the relationship between the crystallinity of the GaN film and the polarity of the ZnO substrate, were investigated. Growth at a high temperature (e.g., 800°C) was made possible by using an (In,Ga)N buffer layer, which improved the crystallinity of the GaN films compared with that of GaN films grown directly on a ZnO substrate. Ion scattering, i.e., coaxial impact-collision ion scattering spectroscopy, and electron beam channeling, i.e., convergent beam electron diffraction, profiles revealed that the GaN films grown on c(+)-and c(-)-ZnO substrates with an (In,Ga)N buffer layer had a (0001) surface (i.e., c(+) polarity). That is, polarity inversion occurs when GaN film is grown with an (In,Ga)N buffer layer on a c(-)-ZnO substrate.

Effects of Ga on the growth of InN on O-face ZnO(0001¯) by plasma-assisted molecular beam epitaxy

“…As the primary reason for the high defect densities observed despite nominal lattice matching, several researchers identified the high chemical reactivity of the group-III metals with ZnO which results in a severe degradation of the interface between these two materials. [9][10][11][12] We have recently found that within a narrow temperature range, InN films of comparatively high structural quality can be synthesized on O-face ZnOð000 1Þ despite the large lattice mismatch between these two materials. 11 To investigate if such a growth window also exists when adding Ga, we compare the structural properties of thin InN and In 0:95 Ga 0:05 N films directly grown on ZnOð000 1Þ at different substrate temperatures.…”