Deep etching of epitaxial gallium nitride film by multiwavelength excitation process using F2 and KrF excimer lasers

The deep etching of GaN(0001) thin films epitaxially grown on Al2O3(0001) has been investigated by laser ablation using F-2 and KrF excimer lasers. The simultaneous irradiation with F-2 and KrF excimer lasers markedly improves etching quality compared with single-KrF excimer laser ablation and provides almost the same quality as that in the case of single-F-2 laser ablation with a high etching rate. Additionally, the present method achieves the deep etching of a GaN film of more than 5 mu m in depth with steep side walls at an angle of 87 degrees by changing the laser incidence angle.