Masaki Funabashi, Koji Hiraiwa, Kazuaki Nishikata, Nobumitsu Yamanaka, Norihiro Iwai, Akihiko Kasukawa
Waveguide photodiodes hold promise for long-wavelength applications in optical subscriber networks, and this paper reports on the methods used in their design and manufacture, as well as on the results obtained from prototype devices. With a view to the improved productivity and reduced cost associated with volume manufacture, the prototype were fabricated by a full-wafer process using 2-inch InP wafers. The device showed an extremely low dark current value --only a few hundred pA --and high responsivity --0.95 A/W or above. Characteristic deviation within wafers was evaluated, confirming that 2-inch wafers having high in-wafer uniformity with respect to dark current and responsivity could be produced with high yield. The devices had a frequency bandwidth of approximately 4 GHz and a vertical coupling tolerance of 4µm, with low intermodulation distortion and high reliability.