Effect of substrate temperature on properties of AlN buffer layer grown by remote plasma ALD

Abstract

Aluminum nitride (AlN) thin film has considerable properties, which makes it advantages for a variety of applications. AlN films were prepared by remote plasma atomic layer deposition (RP-ALD) with the growth temperature of 100 to 450 °C. The properties of AlN films with various growth temperatures were studied systematically. In addition, AlN/GaN layers deposited on sapphire (Al2O3) substrates were also investigated. The AlN/GaN interfaces and AlN/Al2O3 interfaces characteristics were analyzed. The optical property of GaN films prepared on sapphire substrates with and without AlN buffer layer were identified by photoluminescence measurement. The experiment result shows that crystal AlN films became to present at 250 °C with a hexagonal wurtzite structure. X-ray photoelectron spectroscopy investigation shows that AlN films contain Al-O, Al-O-N complexes and Al-Al metallic aluminum bonds except the main Al-N bond confirmed by high resolution Al 2p and N 1 s spectra. High-resolution transmission electron microscopy measurement reveals sharp interfaces of AlN/Al2O3 and AlN/GaN. The obtained lowest lattice mismatch of AlN/Al2O3 and AlN/GaN are 11.0% and 2.1%, respectively. Photoluminescence measurement further confirms that AlN buffer layer enhances the quality of GaN grown on sapphire substrates. High quality AlN/GaN layers prepared by RP-ALD provides a promising pathway towards high quality GaN-based devices.