All‐optical bistability is demonstrated in GaAs/AlGaAs multiple quantum well microresonators fabricated by SiCl 4 reactive ion etching. A fabrication process has been developed in order to obtain low threshold bistability. The studied samples are two‐dimensional 15×15 arrays of cylindrical microresonators of 4 μm diam and 6 μm height. Owing to lateral carrier and light confinement, bistability is observed with a strongly reduced threshold power, below 100 μW. This result was obtained without post‐etching surface treatment. The low bistability threshold suggests that the surface recombination rate is reasonably small, possibly due to some self‐passivation occurring during the etching process.