Abstract: Wet chemical etching using phosphoric acid/hydrogen peroxide solution on GSMBE grown InGaAs and InAlAs on（001）InP were studied.Results show uniform etch speed and crystallographic edge profile.The etch rate decrease exponentially with increasing dilution ratio,yet the surface morphology remains the same.Etch rate increases and then decreases with a smooth surface morphology as H₂O₂ concentration increases.And the increase of H₃PO₄ concentration gives rise to similar change in etch rate,with a coarser surface.The mechanisms are also discussed.