Kinetic, crystallographic, and optical studies of GaN and AlxGa1-xN thin films grown on Si(111) by pulsed reactive crossed-beam laser ablation using liquid alloys and N-2 or NH3

High quality GaN and AlxGa1-xN films have been grown by reactive crossed-be am pulsed laser deposition at 248 nm (KrF) using liquid Al-Ga alloy targets and a synchronous gas pulse on 7x7 reconstructed Si(111) substrates. The g rowth kinetics and their effect on the optical properties were studied in d etail. The growth rates were lower and the optical properties were superior for GaN films grown with N-2 than when NH3 was used as the nitriding sourc e. The ratio of Ga to Al in the alloy was reproduced in AlxGa1-xN films whe n using NH3, but was in general lower when using N-2. These findings can be explained by the lower reaction rate of Ga with N-2 and the high vapor pre ssure of Ga at the adopted substrate temperatures. (C) 2000 American Instit ute of Physics. [S0021-8979(00)08313- 4].