Wet chemical etching of Al_(0.65)Ga_(0.35)N in aqueous KOH solutions

摘要

We have investigated wet chemical etching of Al_(0.65)Ga_(0.35)N in 20% (by weight) aqueous KOH solutions at 85, 95 and 102 ℃. The etch rates were 0.48, 0.64 and 0.96 μm/min, respectively. Scanning electron microscope, atomic force microscopy, Auger electron spectroscopy and x-ray photoelectron spectroscopy were employed to characterize the surface morphology and stoichiometry before and after wet chemical etching. Experimental results show that aqueous KOH solutions can effectively etch Al_(0.65)Ga_(0.35)N. SEM results show that the root-mean-square (rms) roughness increased from 16.189 to 50.496 nm. Degradation in surface smoothness is attributed to selective anisotropic wet chemical etching. The AES measurements show that after the untreated sample was wet chemical treated in a 20% KOH solution at 85 ℃ for 15 seconds, the oxide formed in the surface was removed and a lower content of oxide layer near the surface was formed and the N content is higher. XPS measurements show that the banding energies of Ga 3d shifted to low energy direction after the untreated sample was successively wet chemical treated. It indicated that the atom Ga tended to form Ga-N rather than Ga-O bonding on the surface after KOH solution treatment. The damage and oxide layer induced by dry etching processes was effectively removed by wet chemical treatment and the damage surface was refreshed.