Pendeo-epitaxial growth of thin films of gallium nitride and related materials and their characterization
Monocrystalline GaN and AlxGa1-xN films have been grown via the pendeo-epitaxy (PE)(1) technique with and without Si3N4 masks on GaN/AlN/6H-SiC(0 0 0 1) and GaN(0 0 0 1)/AlN(0 0 0 1)/3C-SiC(1 1 1)/Si(1 1 1) substrates using organometallic vapor phase deposition. Scanning and transmission electron microscopies were used to evaluate the external microstructures and the distribution of dislocations, respectively. The dislocation densities in the PE grown films were reduced at least five orders of magnitude relative to the initial GaN seed layers. Tilting to 0.2 degrees in the portion of the coalesced GaN epilayers grown over the silicon nitride masks was observed via X-ray diffraction. Neither tilting nor low angle boundaries were observed within areas of coalescence in the material grown on substrates without the masks. The strong, low-temperature PL band-edge peak at 3.45 eV with a FWHM of 17 meV was comparable to that observed in PE GaN films grown on 6H-SiC(0 0 0 1). The band-edge in the GaN grown on AlN(0 0 0 1)/SiC(1 1 1)Si(1 1 1) substrates was shifted to a lower energy by 10 meV, indicative of a greater tensile stress. (C) 2001 Elsevier Science B.V. All rights reserved.