High-pure AlN crystalline thin films deposited on GaN at low temperature by plasma-enhanced ALD

Aluminum nitride (AlN) thin film has been considered one of the most promising candidates for gate insulating layer of GaN-based HEMT devices. To reach the highest performance of devices, it is still necessary to further reduce the defect density at the interface and within the film of the AlN insulating layer, as well as to develop low temperature processes for good compatibility. In this work, by adopting an extra Ar plasma pulse in the plasma-enhanced atomic layer deposition (PEALD) process cycle, crystalline AlN thin films were deposited on Gallium Nitride (GaN) substrates at a temperature as low as 200 degrees C and have almost no C and O contaminations detectable in the films. The atomic structure, surface morphology and chemical component of the AlN films have been characterized systemically, showing the great potential of application in GaN devices as gate insulating or passivation layers.