Etching results using the solution system of citric acid/H2O2 and de-ionized H2O/buffered oxide etch are shown to provide good selective wet etching of AlGaAs/GaAs structures. For AlxGa1-xAs (x≪0.5) layers the selective characteristics of each Al composition strongly depend on the volume ratio of the citric acid/H2O2 solution. The turning volume ratio of the solution, at which etching starts, sensitively depends on Al composition. Additionally, the etch rate of AlyGa1-yAs (y≫0.7) quickly decreases with decreasing Al composition in de-ionized H2O/buffered oxide etch solution, providing a high degree of etching selectivity. These simple selective etching processes have been applied to define AlAs/GaAs distributed Bragg reflector mesas in a vertical-cavity surface-emitting laser structure. © 1998 American Vacuum Society.