Crystallographic dependence of the lateral undercut wet etching rate of InGaP in HCl

The crystallographic dependence of the lateral etch rate in 12 M HCl of InGaP lattice matched to GaAs has been measured. The etch rate at 20 °C is found to have twofold rotational symmetry about [100] and varies between <0.01 μm/min for mesas oriented along 〈011〉 directions and ∼0.9 μm/min for mesas 55° and 125° from [011] towards [01̄1]. Etch fronts consist of {111}A planes. The etch rate also depends on the direction of etch step flow, suggesting that reconstruction plays an important role during InGaP wet etching.