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Reactions of Cl with GaAs: A theoretical understanding of GaAs-surface etching.

The interaction of chlorine with compound semiconductors is essential for the etching processes. In order to elucidate the etching mechanism, we have investigated the reactions of Cl atoms with both the GaAs surface and the bulk region, using the first-principles pseudopotential method. It is found that the adsorption of Cl atoms does not significantly weaken the Ga-As back bonds in the topmost layers. We propose two reactions of Cl atoms which initiate the breakup of the GaAs crystal: an exchange reaction between Cl and As atoms and insertion of Cl atoms in Ga-As bonds. The etching processes are discussed in terms of the calculated results.