Effect of AlN buffer layer thickness on the properties of GaN films grown by pulsed laser deposition

Abstract

The GaN films are grown by pulsed laser deposition (PLD) on sapphire, AlN(30nm)/Al2O3 and AlN(150nm)/Al2O3, respectively. The effect of AlN buffer layer thickness on the properties of GaN films grown by PLD is investigated systematically. The characterizations reveal that as AlN buffer layer thickness increases, the surface root-mean-square (RMS) roughness of GaN film decreases from 11.5nm to 2.3nm, while the FWHM value of GaN film rises up from 20.28arcmin to 84.6arcmin and then drops to 31.8arcmin. These results are different from the GaN films deposited by metal organic chemical vapor deposition (MOCVD) with AlN buffer layers, which shows the improvement of crystalline qualities and surface morphologies with the thickening of AlN buffer layer. The mechanism of the effect of AlN buffer layer on the growth of GaN films by PLD is hence proposed.