Pulsed KrF laser deposited GaN/TiN/Si(111) heterostructures by sequential TiN and liquid Ga laser ablation

Abstract.

GaN/TiN heterostructures were deposited on 4° miscut Si(111) substrates by pulsed KrF laser ablation of TiN through vacuum, followed by reactive pulsed KrF laser ablation of liquid Ga through 70–75 mTorr of microwave-activated NH₃. Deposition temperatures of 950 °C and 1050 °C were employed for the TiN layer while 900 °C was employed for the GaN layer. The targets were positioned 5 cm from the substrate and ablated by using a reimaging beamline at a nominal energy density of 3–4 J/cm². X-ray diffraction (XRD) revealed a highly textured heterostructure with GaN(0001)//TiN(111)//Si(111) and with a rocking curve width for both GaN(0001) and TiN(111) equal to ∼1.1°. The mosaic spread through the TiN(001) reflection was ∼1.3°, whereas that of the GaN(101_1) was undetectable because of low S/N. Scanning electron microscopy revealed large oriented 10 μm-sized hexagonal crystallites decorating large depressions in the TiN film with many smaller pits also present. The effect of substrate processing and TiN film processing on pit formation was explored.