Roughness and damage of a GaAs surface after chemically assisted ion beam etching with Cl2/Ar+

The surface roughness and the near surface damage of semiconductor structures after etching are important criteria for applications in the field of opto- and micro-electronics. The chemically assisted ion beam etching (CAIBE) causes a surface roughness higher than that for ion beam etching (rms < 0.2 nm) but lower than that for chemical dry etching (rms > 5 nm). Compared to the roughness an inverse behaviour is observed for the damage of the near surface region. Physical processes like sputtering, implantation or diffusion cause heavy damage. The higher the chemical assistance of the physical ion etching, achieved at a high chlorine pressure or a high surface temperature, the higher the etch rate and the lower the damage. For the CAIBE process an average damage depth of about 200 nm was measured. The damage was evaluated by photoluminescence spectroscopy measurements on a multi quantum well structure of Al0.35Ga0.65As/GaAs after bevel etching of the surface to improve the depth resolution of the damage measurements.