Fabrication of two dimensional GaN nanophotonic crystals (31)

The authors have investigated chlorine based inductively coupled plasma etching of GaN by using different gas mixtures of Ar, Cl2, and N2. The etch mechanism and N2 role have been studied. We found that both ion energy and ion current density are important. The N2 plays a multiple role in etching GaN, chemical reaction, and ion bombardment. A reliable process to fabricate GaN nanophotonic crystals has been developed. Plasma conditions have been optimized toward a balance of ion current density, ion energy, and chemical species density. As a result, flat bottom, anisotropic photonic crystal with a=215 nm d=129 nm has been fabricated at an etch rate of 320 nm/min and an etch depth of 650 nm. For comparison, an etch rate of 530 nm/min has been obtained in etching trench lines down to 1.61 µm deep with a width of 500 nm. The developed process has been used to fabricate GaN photonic crystal (PC) waveguides for 1.55 µm wavelength. Transmission measurements reveal the M stop band in hole type PC and illustrate the feasibility of the fabrication process.