THE ETCHING OF GALLIUM-ARSENIDE WITH IODINE MONOCHLORIDE

The reaction of GaAs(100) with iodine monochloride has been studied at ICl pressures between 0.10 and 0.80 Torr and in the temperature range from 100 to 300-degrees-C. At low temperatures the etch rate is first order in ICl, and decreases as the temperature increases, dropping to a minimum at about 140-degrees-C. Above this temperature the order of the reaction drops below 1, and the etch rate increases with increasing temperature. This complex behavior is analyzed in terms of two distinct mechanisms. At low temperatures the negative temperature dependence is explained by a physisorption controlled mechanism and is characterized by the rate law Etch rate = 10(-5.8+/-0.2) mum min-1 Torr-1 e+(47+/-1 kJ mol-1/RT)P(ICl) At higher temperatures the data is consistent with a mechanism in which the ICl is dissociatively adsorbed on the GaAs. At low pressures the rate law is given by Etch rate = 10(5.6+/-1.7) mum min-1 Torr-1 e-(39+/-17 kJ mol-1/RT)P(ICl) At higher pressures the dissociative adsorption becomes reversible, the order of the reaction becomes one-half, and the rate law takes the form Etch rate = 10(4.4+/-0.1) mum min-1 Torr-1/2 e-(33+/-1 kJ mol-1/RT) square-root P(ICl)