Wide-bandwidth InP/InGaAsP/InGaAs avalanche photodiodes grown by chemical beam epitaxy

Efforts to utilize existing fiber cables for the ever-expanding telecommunications marketplace has stimulated efforts to increase the circuit capacity of lightwave systems. One of the most obvious approaches has been to increase the rate of transmission and this appears to be leading to what may be referred to as the "multigigabit/s era". In order to achieve high receiver sensitivities at these high bit rates it is essential that avalanche photodiodes (APDs) with multigigahertz bandwidths be developed. To date, the SAGM-APD structure has demonstrated the highest operating frequencies. It consists of a wide-bandgap multiplication region and a narrow-bandgap absorbing layer separated by a transition region to improve the frequency response. In this paper we report InP/InGaAsP/InGaAs SAGM-APDs grown by chemical beam epitaxy that have exhibited bandwidths as high as 8 GHz and gain-bandwidth products of 70 GHz. We also discuss the factors that determine their frequency response.