Comparative study of NH4OH and HCl etching behaviours on AlGaN surfaces

Abstract A controlled AlGaN surface preparation method avails to improve the performance of GaN-based HEMT devices. A comparative investigation of chemical treatments by (1:10) NH 4 OH:H 2 O and (1:10) HCl:H 2 O solutions for AlGaN surface preparation by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) is reported. The XPS data clearly reveal that the native oxide on AlGaN was composed of Al 2 O 3 , Ga 2 O 3 and NO compounds. These compounds were etched off partially or completely by both the chemical treatments, namely NH 4 OH or HCl solutions, independently. The HCl treatment etches out Al 2 O 3 completely from native oxide unlike NH 4 OH treatment. The HCl treatment results in larger amount of carbon segregation on AlGaN surfaces, however it removes all oxides’ compounds faster than NH 4 OH treatment. The AFM results reveal the improvement of surface morphology by both the chemical treatments leading to the surface roughness RMS values of 0.24 nm and 0.21 nm for NH 4 OH and HCl treated AlGaN layers, respectively.