Growth of a-Plane GaN Films on r-Plane Sapphire by Combining Metal Organic Vapor Phase Epitaxy with the Hydride Vapor Phase Epitaxy**Supported by the National Natural Science Foundation of China under Grant No 61204006, the Fundamental Research Funds for the Central Universities under Grant No 7214570101, and the National Key Science and Technology Special Project under Grant No 2008ZX01002-002.

Abstract

Hydride vapor phase epitaxy (HVPE) is utilized to grow nonpolar a-plane GaN layers on r-plane sapphire templates prepared by metal organic vapor phase epitaxy (MOVPE). The surface morphology and microstructures of the samples are characterized by atomic force microscopy. The full width at half maximum (FWHM) of the HVPE sample shows a W-shape and that of the MOVPE sample shows an M-shape plane with the degree of ϕ in the high-resolution x-ray diffraction (HRXRD) results. The surface morphology attributes to this significant anisotropic. HRXRD reveals that there is a significant reduction in the FWHM, both on-axis and off-axis for HVPE GaN are compared with the MOVPE template. The decrease of the FWHM of E2 (high) Raman scattering spectra further indicates the improvement of crystal quality after HVPE. By comparing the results of secondary-ion-mass spectroscope and photoluminescence spectrum of the samples grown by HVPE and MOVPE, we propose that C-involved defects are originally responsible for the yellow luminescence.