Nonselective etching of GaN/AlGaN heterostructures by Cl_2/Ar/BCl_3 inductively coupled plasmas

摘要

A systematic study of the nonselective and smooth etching of GaN/AlGaN heterostructures was performed using Cl_2/Ar/BCl_3 inductively coupled plasmas (ICP). Nonselective etching can be realized by adjusting the BCl_3 ratio in the Cl_2/Ar/BCl_3 mixture (20 percent-60 percent), increasing the ICP power and dc bias, and decreasing the chamber pressure. Surface morphology of the etched heterostructures strongly depends on the gas chemistry and the chamber pressure. Specifically, with the addition of 20 percent BCl_3 to Cl_2/Ar (4:1) gas mixture, nonselective etching of GaN/Al_(0.28)Ga_(0.72)N heterostructures at high etch rate is maintained and the surface root-mean-square (rms) roughness is reduced from 10.622 to 0.495 nm, which is smoother than the as-grown sample. Auger electron spectroscopy (AES) analysis shows that the effective removal of residual oxygen from the surface of AlGaN during the etching process is crucial to the nonselective and smooth etching of GaN/AlGaN herterostructures at high etch rate.