ABSTRACT
C-plane AIN epitaxial film with thickness of 2pm was grown on 2-inch-diameter Cplane sapphire substrate by low-pressure metal organic vapour phase epitaxy (LPMOVPE) without any low-temperature buffer layer. Subsequently, C-plane GaN with thickness of 3 pm was directly grown on the AIN epitaxial film under the growth condition of 500Torr, 1155 °C and 60min using another MOVPE system. Trimethylaluminum (TMA), trimethylgallium (TMG) and ammonium were used as source materials. These MOVPE systems were optimised for AIN and GaN growth individually. Surface morphology measurement of the GaN and AIN was performed using atomic force microscopy (AFM) (Nanoscope III). XRC measurement was also performed to evaluate macroscopic GaN and AIN crystal qualities using a Philips MRD with a Ge(220) monochromator. XRC measurement for the (10-10) plane as well as for XRC for the (0004) plane was performed in order to clarify their overall mosaicity. TEM samples with a thickness of about 50nm for cross-sectional observation were prepared by the focused ion beam (FIB) technique. The observation of structural defects was made by 300kV TEM (Hitachi H-9000UHR). The electron incidence of images was parallel to the [10-10]GaN/AlN direction. Bright field images and the 0002-type and 112 0 -type dark field images were observed in order to clarify the differences in dislocation behaviour between edge type and screw type.
