High Bandwidth Planar InP/InGaAs Avalanche Photodiodes

It is well known that planar InP/InGaAs avalanche photodiodes (APDs) can be used to increase the sensitivity of lightwave receivers used in systems operating at 2 Gbits/s. As lightwave systems move to higher bit rates it is clear that the bandwidth of the APDs must also be increased. We have developed a planar InP/InGaAs APD with high bandwidth (70 GHz gain- bandwidth product) for use in high bit rate lightwave systems. In this paper we will discuss the design, fabrication and performance of the planar APDs. We will show that understanding the equivalent circuit of the APD is required to determine the intrinsic APD bandwidth and that the gain- bandwidth product is a strong function of the heterointerface field.