Etching characteristics of AlxGa1−xAs in (NH4)2Sx solutions

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Abstract
The etching of GaAs and AlxGa1−xAs have been characterized in (NH4)2Sx solution with various excess sulfur concentrations and for temperatures ranging from 20 to 60 °C. The etch rate varies with the concentration of excess sulfur and is highest at 60 °C using a 4% excess sulfur solution. The etch rate of AlxGa1−xAs increases exponentially with increasing Al mole fraction. Activation energies of 19.8 and 15.9 kcal/mole are obtained for GaAs and Al0.3Ga0.7As in 4% (NH4)2Sx, respectively. These high values and the linear time dependence of etch rates signify that the etching process of AlxGa1−xAs in (NH4)2Sx solutions is predominantly reaction‐rate limited. Possible chemical processes involved in the etching and the formation of a passivating sulfur layer are discussed.