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-epit axy (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 o rganometallic vapor phase deposition. Scanning and transmission electron mi croscopies were used to evaluate the external microstructures and the distr ibution 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 coale sced GaN epilayers grown over the silicon nitride masks was observed via X- ray diffraction. Neither tilting nor low angle boundaries were observed wit hin areas of coalescence in the material grown on substrates without the ma sks. The strong, low-temperature PL band-edge peak at 3.45 eV with a FWHM o f 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.