A bistable GaAs–InGaP triangular-barrier optoelectronic switch (TBOS), grown by metalorganic chemical vapor deposition, was fabricated. By introducing avalanche multiplication and carrier confinement into the device operation, S-shaped negative-differential-resistance performances are observed in the current–voltage(I–V)characteristics under normal and reverse operation modes. The TBOS shows a flexible optical function related to the potential barrier height controllable by incident light. The dependence of the carrier transport mechanism on the illumination was investigated. TheI–Vcharacteristics at different temperatures were also discussed. ©1997 American Institute of Physics.