Epitaxy of gallium nitride by HVPE using low temperature intermediate buffer layers deposited by MOVPE

We investigated the use of different GaN and AM buffer layers pre-deposited at low temperature (LT) for the growth of thick GaN layers by Hydride Vapor Phase Epitaxy (HVPE). The layers obtained on LT buffer layers grown by Metal-Organic Vapor Phase Epitaxy (MOVPE) show an excellent homogeneity, good crystalline quality (X-Ray Diffraction (XRD) Full Width at Half Maximum (FWHM) values around 650 arcsec) and the surface morphology (characterized by optical microscopy and atomic force microscopy measurements) is significantly improved compared to layers grown directly on sapphire. The partial replacement of the carrier gas nitrogen by hydrogen leads to a further improvement of the surface morphology and crystalline quality, reaching best XRD FWHM values of 350 arcsec. In contrast, experiments using an amorphous LT-HVPE buffer layer grown in situ show rather poor results.