Semipolar GaN Films on Prism Stripe Patterned a-Plane Sapphire Substrates

Abstract

A semipolar GaN layer was grown on periodic stripe patterned a-plane sapphire substrate fabricated by using two-steps etching process. The stripes in prism shape were inclined with sapphire c-axis in 60 degrees. The orientation relationship between semipolar GaN and sapphire is (0 0 0 2)GaN//()sapphire and []GaN//[]sapphire as defined by selected area diffraction in transmission electron microscopy (TEM). Growth of semipolar GaN on the sidewalls of the prism stripes is evidenced from TEM and X-ray φ scan. The quality of semipolar GaN film is reasonably good as examined with X-ray rocking curves. In addition, TEM and cathodoluminescence results show that the dislocation density in the semipolar GaN is significantly reduced near the film surface.