Amorphous GaN (a-GaN) films were deposited at a low temperature below 500°C by compound-source molecular beam epitaxy (CS-MBE). The relationship between excess Ga and its oxidation in the deposited GaN films is reported. X-ray photoelectron spectroscopy (XPS) revealed that the excess Ga in deposited films was oxidized in the air and converted to gallium oxide. By increasing the substrate temperature, the total amount of gallium oxide in the deposited films decreased due to the reduction of the excess Ga. Cathodoluminescence (CL) intensity from the UV to the blue spectral regions increased with as the amount of gallium oxide in the deposited films decreased.
Articles you may be interested inIn-situ NC-AFM measurements of high quality AlN(0001) layers grown at low growth rate on 4H-SiC(0001) and Si (111) substrates using ammonia molecular beam epitaxy AIP Advances 5, 067108 (2015); 10.1063/1.4922193 Influence of the AlGaN buffer layer on the biaxial strain of GaN epilayers grown on 6H-SiC (0001) by molecularbeam epitaxy J. Appl. Phys. 97, 013524 (2005); 10.1063/1.1826219 Single-phase growth studies of GaP on Si by solid-source molecular beam epitaxy Reactive molecular-beam epitaxy of GaN layers directly on 6H-SiC(0001) Appl. Phys. Lett. 75, 944 (1999);The low-temperature growth of GaN is required to prevent cracks due to thermal expansion. The lower limit of the temperature of the GaN growth by compound source molecular beam epitaxy ͑CS-MBE͒ was estimated using the results of reflection high-energy electron diffraction and atomic force microscopy. The lower limit of the temperature of GaN growth by CS-MBE was investigated and found to be below 450°C. The lower limit is due to the migration of atoms at the surface and the re-evaporation of excess Ga atoms.
GaN films were deposited at the low temperature by compound-source molecular beam epitaxy technique. Structural ordering of the GaN films was investigated using x-ray photoelectron spectroscopy (XPS) and refractive high-energy electron diffraction (RHEED) techniques. XPS spectra show that excess Ga in the films was oxidized. The binding energy of Ga–N bonds in the deposited GaN film is almost equal to that in GaN crystals. On the other hand, the RHEED patterns of the films deposited on SiO2∕(111) indicate that the long-range tetrahedral ordering in deposited GaN is disappeared although those on (111) Si were streaky.
GaN-based electroluminescent devices were fabricated on aluminum substrates at the low-temperature less than 500°C. Purplish-blue emission was observed from the devices driven under pulsed voltage. The aluminum substrate is effective to realize their long lifetime.
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