Abstract

The speed of response of avalanche photodiodes (APDs) can be an important factor in determining the performance of high-bit-rate optical receivers. The most common limitations to detector speed are carrier diffusion, charge pileup at heterointerfaces, which has been observed in heterostructure APDs for use at long wavelengths,¹ RC time constants, and the gain-bandwidth limit. Whereas the first three sources of speed degradation can be made negligibly small by proper device design, the gain- bandwidth product presents a fundamental limitation to device speed. In this paper we discuss the gain-bandwidth limit of InGaAs/InP heterostructure APDs which are rapidly emerging as the most promising devices for use in high-bit-rate long- wavelength (λ < 1.65-μm) optical communication systems. We also develop a means whereby the bandwidth limit of an APD optical receiver can be calculated once the sensitivity of that receiver is determined using only a pin photodetector. Comparison of these calculations to published experimental results will be made.

© 1984 Optical Society of America