GaN metal-oxide-semiconductor diodes with molecular beam epitaxy-Al_2O_3 as a template followed by atomic layer deposition growth

摘要

The interfacial chemical characteristics and electrical properties of the metal-oxide-semiconductor (MOS) diode using molecular beam epitaxy (MBE)-Al_2O_3 as a dielectric template followed by atomic layer deposited (ALD) Al_2O_3 on hydrochloric acid (HC1) solution-cleaned GaN were studied and correlated. The results are compared with those using ALD-Al_2O_3 as the dielectrics. With in situ X-ray photoelectron spectroscopy (XPS) analyses, a significant amount of residual Cl on the HCl-cleaned GaN surface was detected. The residual Cl was reduced by annealing at 300 and 670℃, two temperatures for ALD and MBE-Al_2O_3 growth, respectively, with the amount being further reduced by the 670℃ annealing. The electrical characteristics were consistent with the XPS analyses; well-behaved capacitance-voltage (C-V) characteristics were obtained in the MBE-template sample, while appearance of a bump in the C-V curves was observed in the ALD-sample without the MBE template.