Abstract
We have grown epitaxial GaN and ZnO films on sapphire and silicon substrates, and investigated the possibility of forming channel waveguides utilizing the effect of thin-film-induced index change. Two-dimensional confinement of light was clearly observed in the channel region of GaN defined by a SiN cladding layer of a stripe window pattern. The lateral confinement of light in the window region indicates that the effective guide index in the window region of GaN is higher than that in the SiN-loaded outer region. We carried out numerical analyses on the various possible effects that might contribute to the overcompensation of the negative loading effect of a SiN cladding window. This includes the photoelastic, piezoelectric, and electro-optic effects in GaN induced by a SiN window layer. It is suggested that the observed phenomenon can be ascribed to a combination of both the photoelastic and electro-optic effects, and especially that the spontaneous polarization field in GaN might play an important role in forming a channel waveguide in the window region. (Author)