All-optical bistability is demonstrated in GaAs/AlGaAs multiple quantu
m well microresonators fabricated by SiCl4 reactive ion etching. A fab
rication process has been developed in order to obtain low threshold b
istability. The studied samples are two-dimensional 15X15 arrays of cy
lindrical microresonators of 4 mu m diam and 6 mu m height. Owing to l
ateral carrier and light confinement, bistability is observed with a s
trongly reduced threshold power, below 100 mu W. This result-was obtai
ned without post-etching surface treatment. The low bistability thresh
old suggests that the surface recombination rate is reasonably small,
possibly due to some self-passivation occurring during the etching pro
cess.