Fabrication of Patterned Sapphire Substrate by Wet Chemical Etching for Maskless Lateral Overgrowth of GaN

Abstract

The grooved -plane sapphire substrates were first systematically investigated by wet chemical etching, with and a mixture as the etchants. The structural and morphological characteristics of the grooved sapphire with mask stripes along the and directions, respectively, were studied under different etching time and temperatures by scanning electron microscopy (SEM). Two kinds of groove shapes are obtained. One is a V-groove whose two sidewalls are both formed by a single facet. The other is a U-groove whose one sidewall consists of two or three facets, and the other sidewall is composed of a single facet. SEM cross-sectional images show symmetrical sidewall facets with stripes along the sapphire direction and asymmetrical sidewall facets with stripes along the sapphire direction. The etching depth is linear with the etching time. The activation energies of etching reaction are evaluated in the temperature range . It is confirmed that sapphire with stripes along the direction is suitable for lateral epitaxial overgrowth of low-threading-dislocation GaN films.