Growth of AlN films on Si (100) and Si (111) substrates by reactive magnetron sputtering

GaN has shown great potential for high-power high-frequency electronic devices and short-wavelength optical devices. To integrate GaN-based optoelectronic devices with Si-based electronic devices and reduce the cost, it is desirable to grow epitaxial GaN thin films and device structures on the Si substrate. However, a proper buffer layer is essential for epitaxial growth of GaN films on Si substrate due to large mismatch between them in the area of lattice constant, thermal expansion coefficient and chemistry feature. In the present work, the growth of AlN buffer layer was studied. Wurtzite aluminum nitride thin films were grown on Si (111) and Si (100) substrates using reactive sputtering deposition under different discharge powers. X-ray diffraction (XRD) patterns showed that full width at half maximum (FWHM) of AlN (0002) peak grown on Si (111) substrates was smaller than that grown on Si (100) substrates. Vibrational characterization by Fourier transform infrared spectroscopy (FTIR) revealed that the stress in the AlN films deposited on Si (111) substrates was also smaller than that deposited on Si (100) substrates. For Si (100) substrates, the large lattice mismatch between AlN (0001) and Si (100) is a main contribution to the large strain in the formed films. For Si (111) substrates, the strain in the films deposited on Si (111) largely depends on the discharge power in sputtering, and the strain due to defects and thermal mismatch contributes largely to the residual strain in the deposited films.