In order to achieve high optical sensitivity and low holding power, a wide-gap carrier confinement layer was introduced into the collector region of an n-p-n-heterostructure optoelectronic switch. A similar device without the confinement layer was also fabricated to demonstrate the performance improvement. Both devices were found to have bistable electrical states: a high-impedance OFF state connected to a low-impedance ON state by a region of negative differential resistance. The functional characteristics were based on avalanche multiplication. (c) 2006 The Electrochemical Society.