An integrated optoelectronic multiplier based on GaAs optoelectronic device technology, is proposed. The key element is an optoelectronic half-adder logic gate, which is composed of only two GaAs metal-semiconductor-metal photodetectors (MSM-PD's). It operates with a single clock delay, less than 100 ps. An optoelectronic full-adder and a multiplier are also composed of half-adders and surface-emitting laser-diodes (SEL's). Cascadable gates with optical interconnections are integrated. Utilizing improved device fabrication technology, an optoelectronic high-speed multiplier with a minimum number of gates will be realized in LSI.