Arrays of all‐optical bistable devices have been fabricated by reactive ion etching (RIE). The vertical Fabry–Pérot structures grown by organometallic vapor‐phase epitaxy include GaAs/Ga0.7Al0.3As multiple quantum wells and AlAs/Ga0.9Al0.1As Bragg reflectors and exhibit optical bistability under moderately focused laser excitation (10–30 μm spot diameter). After RIE, the arrays show a reduced bistability threshold of 70 μW on 4 μm diameter and 5.7 μm high microresonators. This suggests that surface recombination does not play a significant role. This and the absence of degradation of the etched AlAs layers for more than 10 months indicate a self‐passivation of the vertical surfaces during the etching process. Selective plasma etching reveals the presence of a thin cylindrical film clearly visible with a scanning electron microscope. The composition of this film is analyzed by Auger spectroscopy.