Epitaxial CBN growth for fast electro-optic tunable devices

摘要

In this study, we report for the first time the epitaxial growth of CBN thin films on Magnesium Oxide (MgO) substrates for optical device applications. A high deposition temperature ( ≥ 800℃) is required to obtain the epitaxial growth of CBN films. A parametric study is proposed in order to elaborate CBN thin films with a crystal structure as close as possible to that of a CBN bulk single crystal and with good optical characteristics. In particular, a low oxygen pressure (1 mTorr) allows synthesizing high-quality CBN thin films with an out-off plane lattice parameter comparable to the one of CBN bulk material at low surface roughness. The optical characterization of the high-quality CBN thin films reveals a high optical transmission ( ≥ 85 %) and a refractive index equal to 2.22 at 1.55 μm for certain deposition conditions. These optical properties clearly indicate the potential of CBN thin films for waveguide applications. This work presents a significant first step toward the integration and the potential use of CBN films for optical device applications.