Fabrication of ZnO photonic crystals by nanosphere lithography using inductively coupled-plasma reactive ion etching with $CH4/H2/Ar$ plasma on the ZnO/GaN heterojunction light emitting diodes

This article reports fabrication of $n$-ZnO photonic crystal/$p$-GaN light emitting diode (LED) by nanosphere lithography to further booster the light efficiency. In this article, the fabrication of ZnO photonic crystals is carried out by nanosphere lithography using inductively coupled plasma reactive ion etching with $CH4/H2/Ar$ plasma on the $n$-ZnO/$p$-GaN heterojunction LEDs. The $CH4/H2/Ar$ mixed gas gives high etching rate of $n$-ZnO film, which yields a better surface morphology and results less plasma-induced damages of the $n$-ZnO film. Optimal ZnO lattice parameters of 200 nm and air fill factor from 0.35 to 0.65 were obtained from fitting the spectrum of $n$-ZnO/$p$-GaN LED using a MATLAB code. In this article, we will show our recent result that a ZnO photonic crystal cylinder has been fabricated using polystyrene nanosphere mask with lattice parameter of 200 nm and radius of hole around 70 nm. Surface morphology of ZnO photonic crystal was examined by scanning electron microscope.