Low-temperature high-quality epitaxial AlN films deposited by plasma-enhanced atomic layer deposition

This work demonstrates low-temperature epitaxial growth of aluminum nitride (AlN) films by plasma-enhanced atomic layer deposition (PEALD). AlN, an ultra-wide bandgap semiconductor with broad applications in optoelectronics and high-power electronics, was deposited on gallium nitride (GaN) templates (GaN-on-sapphire). Single-crystal quality films were obtained at a remarkably low temperature of 300°C while avoiding additional in situ energetic plasma exposures or ex situ annealing steps, which can damage the film. High crystalline quality is indicated by narrow x-ray diffraction rocking curves of 288arc sec (0.08°) and 497arc sec (0.138°) for 10 and 70nm films, respectively. Continuous high-quality epitaxial growth was maintained across the full film thickness, even at 70nm, as confirmed by high-resolution transmission electron microscopy and selected area electron diffraction. Atomic force microscopy revealed smooth surface morphologies with an average roughness below 1nm. The demonstrated epitaxial quality over the 10–70nm thickness range, achieved at only 300°C by a PEALD process, enables opportunities for III-nitride integration into thermally sensitive processes (e.g., silicon technology) and into GaN-based devices.