Tunable UV laser induced digital etching of GaAs: wavelength dependence of etch rate and surface processes

The wavelength dependence of etch rate in digital etching of GaAs employing Cl2UV laser system and its surface processes are discussed. The characteristic wavelength dependence on etch rate is divided into two regions, approximately 23 or 13 monolayer/cycle, which are identical to regions where Ga trichloride or Ga monochloride forms as the Ga-containing etching products, respectively. These results are well explained by a model involving the photodissociation of physisorbed chlorine layer or chemisorbed GaCl-like layer.