A-plane GaN microchannel epitaxy on r-plane sapphire substrate using patterned graphene mask

a-plane GaN microchannel epitaxy was performed using a patterned graphene mask. As a result, graphene mask was found useful to grow thin lateral growth because graphene has no vertical bonds. It reduces strain in the laterally grown layer while a large strain is usually produced in conventional heteroepitaxy. Graphene mask could bring a thin MCE layer, which was as thin as 120 nm, in the growth mode similar to Frank-van der Merwe mode. Full width as half maximum of omega-scan of X-ray diffraction measurement of the layer was as narrow as 250 arcsec, which was attained without use of low-temperature buffer layer. Etch pit etching shows that two kinds of pits were produced; one corresponded to bunched steps originated from the ordinal heteroepitaxy over the holes of graphene mask, the other is the dislocations which remained in the final connecting points of individual growth islands. The densities of these pits were measured as large as 3-4 x 10(6)cm(-2).