Abstract

Gallium Nitride (GaN) is an interesting direct wide-bandgap optical III-Nitride material with attractive properties such as broad transparency through Visible and IR wavelengths [1], and possesses second-order non-linearity, with reasonably high third-order non-linearity [2]. This makes it an attractive candidate for integrated on-chip photonics applications over a broad wavelength window for different linear and nonlinear applications. GaN is typically grown via heteroepitaxy on substrates such as Sapphire, Silicon (Si), and Silicon Carbide (SiC). Growing reasonably thin GaN (<=500 nm) required for photonics applications on these substrates is a challenging problem. In this work, excellent quality 500 nm GaN is grown on Sapphire substrate, with (002) ω scan FWHM of 0.14°, and RMS roughness of 0.4 nm, best reported so far for photonics applications [1]. Further, we demonstrate highefficiency fiber-chip grating couplers with the efficiency of -4.1 dB/coupler, best reported so far in both GaN-on-insulator and GaN on sapphire platform.

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