GaN freestanding waveguides on Si substrate for Si/GaN hybrid photonic integration

Abstract

Combination of GaN devices with Si devices is promising for the future hybrid integration in optical MEMS such as embedded light sources with electronic circuits. However, GaN optical waveguides are not directly formed on Si substrate because the refractive index of GaN is lower than that of Si. In this research, a GaN layer is grown epitaxially on a Si substrate and GaN freestanding waveguides are fabricated on the Si substrate by etching the Si substrate with XeF2. The waveguides are supported by bridge structures. Light wave propagation is simulated using finite-difference time-domain (FDTD) method. The GaN waveguides are patterned by electron beam lithography using a Cl2 plasma and the etching properties are examined. The waveguide properties such as loss are measured at blue and infrared wavelengths.