Low damage atomic layer etching technology for gate recessed fabrication

In this work, the damage induced by etching to AlGaN surface employing atomic layer etching (ALE), which use Cl₂ plasma and Ar plasma for etching and removal, compared with conventional etching method was investigated. The Hall-effect measurements indicate that a higher two-dimensional electron gas (2DEG) concentration of 1.54 × 10¹³ cm⁻² is achieved and an electron mobility of 1756 cm²/V is obtained on the ALE sample by reducing the bombardment of BCl₂⁺ and BCl ⁺ on the surface. Simultaneously, the damage caused by ALE to the etching surface is lower than the conventional etching method according to Raman spectroscopy analyses and atomic force microscopy (AFM) scans. The X-ray photoelectron spectroscopy (XPS) spectrum and Transmission Electron Microscope (TEM) measurements were further carried out to prove that ALE process results in a higher 2DEG concentration due to maintaining stable Al composition and inducing lower damage on the surface.