Crystalline AlN Interfacial Layer on GaN Using Plasma-Enhanced Atomic Layer Deposition

In this study, we report on the deposition of a highly crystalline AlN interfacial layer on GaN at 330 degrees C via plasma-enhanced atomic layer deposition (PEALD). Trimethylaluminum (TMA) and NH3 plasma were used as the Al and N precursors, respectively. The crystallinity and mass density of AlN were examined using X-ray diffraction (XRD) and X-ray reflectivity (XRR) measurements, respectively, and the chemical bonding states and atomic concentrations of the AlN were determined by X-ray photoelectron spectroscopy (XPS). The AlN/n-GaN interface characteristics were analyzed using TOF-SIMS and STEM, and the electrical characteristics of the AlN were evaluated using metal-insulator-semiconductor (MIS) capacitors. The PEALD process exhibited high linearity between the AlN thickness and the number of cycles without any incubation period, as well as a low carbon impurity of less than 1% and high crystal quality even at a low deposition temperature of 330 degrees C. Moreover, the GaN surface oxidation was successfully suppressed by the AlN interfacial layer. Furthermore, enhanced electrical characteristics were achieved by the MIS capacitor with AlN compared to those achieved without AlN.