Effects of Nano- and Microscale SiO₂ Masks on the Growth of a-Plane GaN Layers on r-Plane Sapphire

Abstract

We report on the combined effects of a-plane GaN layers on a nanoscale patterned insulator on an r-plane sapphire substrate and epitaxial lateral overgrowth (ELOG) techniques. The fully coalescent a-plane GaN layer using nano- and microscale SiO2 masks showed the formation of nano- and microscale voids on the masks, respectively. Atomic force microscopy (AFM) measurements revealed a surface roughness of 0.63 nm and a submicron pit density of ∼7.8 ×107 cm-2. Photoluminescence (PL) intensity was enhanced by a factor of 9.0 in comparison with that of a planar sample. Omega full-width at half-maximum (FWHM) values of the (112̄0) X-ray rocking curve along the c- and m-axes were 553 and 788 arcsec, respectively. A plan-view cathodoluminescence (CL) mapping image showed high luminescence intensity on the SiO2 masks.

Electrical characteristics of a‐plane low‐Mg‐doped p‐GaN Schottky contacts

“…The c ‐plane samples show larger qϕ B around 2.1 eV, and S values are −0.0564 and 0.0576 from the I – V and from PR characteristics, respectively. Recently, smoother surfaces were obtained even for a ‐plane p‐GaN by using an ELOG technique . It is expected that improvement of crystal quality may promise single planes Schottky contacts and serve as better rectification characteristics.…”