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

Films of aluminum nitride (AlN) with thicknesses in the range from 200 to 3600 Å have been deposited at 1050°C by low-pressure MOCVD. Using an alternative precursor, tritertbutylaluminium (Bu^t₃Al), and ammonia (NH₃), we have grown AlN on sapphire (c-Al₂O₃). At a growth rate of 0.35 μm/h, the FWHM of the rocking curve measured by X-ray diffraction was below 320 arcsec. Therefore, we used the thin AlN films as buffer layers for the deposition of gallium nitride (GaN) at 950°C using triethylgallium (Et₃Ga). 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.