Pulsed laser deposition of epitaxial AlN, GaN, and InN thin films on sapphire(0001)

Abstract

Epitaxial aluminum nitride (AlN), gallium nitride (GaN), and indium nitride (InN) films were grown by pulsed laser deposition on sapphire(0001) substrates in high vacuum and in a nitrogen ambient of a few mTorr. The films were analyzed using X-ray diffraction, scanning electron microscopy, atomic force microscopy, and room temperature van der Pauw-Hall measurements. The AlN films were single crystalline with AlN(0001)‖sapphire(0001) and AlN[11̄00]‖sapphire[112̄0]. The GaN films were also single crystalline with the same orientation as the AlN films. The InN films were found to have a preferred crystalline orientation with InN(0001)‖sapphire(0001) and InN[11̄00]‖sapphire[101̄0]. The AlN films were insulating. The GaN film grown in high vacuum had an n-type carrier concentration of 1 × 10 18 cm −3 and a mobility of 300 cm 2/V · s. The GaN film grown in 10 mTorr of N 2 had a p-type carrier concentration of 7.5 × 10 18 cm −3 and a mobility of 150 cm 2/V · s. The InN films grown in high vacuum and 5 mTorr of N 2 were both p-type with carrier concentrations of 6.5 × 10 20 and 4.7 × 10 19 cm −3, and mobilities of 30 and 240 cm 2/V · s, respectively.