Non-polar GaN/AlN superlattices on A-plane AlN (500nm) buffer layers grown by RF-MBE

The growth conditions of A-plane AlN and GaN epitaxial layers by radio-frequency plasma assisted molecular beam epitaxy on R-plane sapphire substrates were investigated. The growth temperature and V/III supply ratio dependency on structural quality and surface roughness was described. The optimum V/III ratio for A-plane GaN and AlN layers was shifted to nitrogen rich side compared to the C-plane layers. A-plane GaN/AlN superlattices (SLs) were also grown on R-plane sapphire substrates. The X-ray diffraction peaks from a primary and a 1st satellite were observed. From a comparison of low temperature photoluminescence peak wavelength between A-plane and C-plane SLs, the built-in electrostatic field originated from spontaneous and piezoelectric polarization is negligible for A-plane SLs.