Nonpolar and semipolar ultraviolet multiple quantum wells on GaN/ sapphire

摘要

The surface morphologies, anisotropic quality and optical properties of nonpolar and semipolar ultraviolet multiple quantum wells (MQWs) structures on GaN/sapphire deposited by metal organic chemical vapor deposition are investigated. The crystal planes of the MQWs are identified as nonpolar (11 (2) over bar0) plane and semipolar (11 (2) over bar2) plane by the 2 theta -omega scan of high-resolution X-ray diffraction (HRXRD). The results of the atomic force microscope and scanning electron microscope show that the surface morphologies of nonpolar and semipolar MQWs structures have obvious differences. The X-ray rocking curves of nonpolar and semipolar MQWs on-axis diffraction planes by HRXRD demonstrate that the semipolar MQWs structure has a better crystalline quality and a weaker anisotropy of crystal quality than nonpolar MQWs structure. The temperature dependence photo-luminescence (PL) spectra reveal that the nonpolar MQWs structure have a stronger yellow band than semipolar MQWs structure. Besides that, the PL spectra of nonpolar MQWs structure also show a blue-shift as temperature increases within a certain range, and then, when the temperature increases continuously, it turns to a red-shift. However, for the semipolar MQWs structure, only the red-shift is observed in PL spectra.