Abstract

Presently GaAs metal-semiconductor-metal (MSM) photodetectors are used for most optical data link systems operating at about 780-850 nm. The MSMs are generally preferred over p-i-n structures due to their low capacitance per unit area. Thus larger detectors can be fabricated that are simple to align and compatible with multimode fibers. If such detectors could be made in silicon, the cost could be further reduced, and the detectors could be integrated with VLSI circuitry. Though the saturation velocity of carriers is about the same in silicon as in GaAs, the weak optical absorption of silicon at these wavelengths causes carriers to be generated deep in the material and thus slows the speed. In MSM structures, the electric field weakens at depths larger than the finger spacing, and these deep carriers cause a long tail to form in the pulse response.

© 1996 Optical Society of America