Excimer laser etching of GaAs, Al xGa 1− xAs and CuInSe 2 in chlorine atmosphere

Abstract

We have studied laser-induced etching (LIE) of GaAs and Al x Ga 1− x As ( x=0.2, 0.66, 0.8) under chlorine atmosphere. In addition, LIE, applied to CuInSe 2 for the first time, was investigated with respect to surface damage production and surface roughness at various laser energy densities. It was found that the etch rates of Al x Ga 1− x As are higher than that of GaAs at the same fluence increasing almost linearly with laser fluence. However, the etch threshold for of Al x Ga 1− x As (55 mJ/cm 2) is lower than of GaAs (85 mJ/cm 2). It could be observed that the background pressure of H 2O and O 2 have no influence on the etch threshold of GaAs and Al x Ga 1− x As during LIE with Cl 2 as reactive gas. Etching of CuInSe 2 shows a complex etch rate dependence suggesting a combination of chemical and physical processes at the surface. Raman scattering was used to show that the surface stoichiometry of CuInSe 2 can be varied from In-rich to Cu-rich by changing different laser parameters. However, in all cases there is crystal damage near the surface of the substrate.