Impact of Surface Treatment on Interface States of ALD Al2O3/GaN Interfaces

Abstract

Two surface treatments of GaN, prior to atomic layer deposition (ALD) of Al2O3, were compared to investigate electronic and chemical interface properties: (1) HCl followed by HF and (2) NH4OH. Constant capacitance deep level transient and optical spectroscopies (CC-DLTS/CC-DLOS) and X-ray photoelectron spectroscopy (XPS) were used to study the impact of the surface treatments on the interface state density (Dit) and the chemical composition of the Al2O3/GaN interface, respectively. It was determined that the HCl/HF treatment resulted in 3–10 times higher Dit near the GaN conduction band, while the NH4OH treatment resulted in nearly 10 times higher Dit deeper in the GaN bandgap. XPS revealed that the HCl/HF treatment left residual adsorbed fluorine atoms at the interface and that the NH4OH treatment resulted in a higher concentration of carbon near the Al2O3/GaN interface. These results are discussed in relation to the relevant literature in attempt to understand the relationship between the chemical composition at the interface and the observed differences in Dit.