Growth of GaN/AlN by low-pressure MOCVD using triethylgallium and tritertbutylaluminium

Films of aluminum nitride (AIN) with thicknesses in the range from 200 to 3600 Angstrom have been deposited at 1050 degrees C by low-pressure MOCVD. Using an alternative precursor, triterbutylaluminium (Bu(3)(t)Al), and ammonia (NH3), we have grown AIN on sapphire (c-Al2O3). At a growth rate of 0.35 mu m/h, the FWHM of the rocking curve measured by X-ray diffraction was below 320 arcsec. Therefore, we used the thin AIN films as buffer layers for the deposition of gallium nitride (GaN) at 950 degrees C using triethylgallium (Et(3)Ga). The improved structural and optical properties of GaN were verified by XRD and Raman, photothermal deflection and photoluminescence spectroscopies. The influence of the buffer layer thickness on the optical properties such as the sub-bandgap absorption, the Raman-active phonons and photoluminescence are presented.