Crystal Quality Improvement of Semipolar (202̄1) GaN on Patterned Sapphire Substrates by In-Situ Deposited SiN Mask

We present our results of (202̄1) GaN growth on (224̄3) patterned sapphire substrates. The substrates are patterned by etching trenches with c-plane-like side-facets. On these facets, the metalorganic vapor phase epitaxy (MOVPE) GaN growth starts in c-direction and forms triangularly shaped stripes eventually coalescing to a (202̄1) oriented layer. Xray rocking curves measured parallel to the stripes of the symmetric (202̄1) reflection show a full width at half maximum of 675 arcsec. Well known from epitaxy of c-plane GaN, an in-situ-deposited SiN mask could help to reduce the defect density further. Systematic investigations of the deposition time and position of the SiN interlayer resulted in a significant improvement of crystal quality confirmed by X-ray and low temperature photoluminescence measurements. Additionally, MOVPE GaN templates with and without SiN mask were overgrown by hydride vapor phase epitaxy. Also now, the SiN interlayer improves the crystal and especially the surface quality of the HVPE layer.