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.

The future trends of optical technologies combined with LSI are reviewed. Present problems of LSI, and the possible solutions to these problems through the merger of the optical technology into LSI are discussed. One of the present trends in interconnection between LSI components is the timeserial approach, originally developed for the optical communication. This method is capable of high speed data transfer. The other is a space-parallel approach, arising from the two-dimensional nature of the light propagation. This approach has the capability of performing parallel processing. A hybrid OEIC, possibly on GaAs, is discussed as an example of future photonic LSI. The lack of key devices is a fundamental barrier to the future improvement of photonic LSI. Direct interaction between photons and electrons is a promissing approach. Some of the Author's ideas to promote the merger of photonics and LSI are proposed.

Analytic expressions for evaluating minimum propagation delay time tpd are derived, using a model which is effective for analysis of the device with a merged structure. Calculated results are in good agreement with experimental ones. Junction modifying coefficient k is newly introduced for the theory. k affects tpd through a variable function of current gains, and a deviation from the Klaassen's theory is pointed out. Role of the pnp transistor on the performance of the I2L gate is emphasized.

A novel amplification mechanism of traveling TM wave on an electron beam within a waveguide structure is proposed. Under boundary constraint of the waveguide, a hybrid coupling of longitudinal plasma wave and transverse guided one occurs to result in traveling instability. The instability refers to a backward traveling amplification. The new amplification in the waveguide due to the interactive coupling between the space charge mode and the waveguide one is firstly pointed out. The analysis is extended to the relativistic energy range to get a large gain. The features and properties are discussed for a wide frequency range as well as a high gain-bandwidth product.