Abstract
Using Germanium as absorption layer for photodetector has highly integrity in IC, which has same wavelength in optical communication. We used critical couple theory combined with traditional p-i-n structure, designed a high frequency response and high bandwidth photodetector. The incident light source would be constructive interference in the cavity, and outside the cavity, the signal would be destructive interference. So the power of incident light source would totally be absorbed by Germanium layer, it could reach up to 90% quantum efficiency and just need a few hundred nanometers Ge absorption layer. Comparing with traditional Ge p-i-n photodetector, our PD’s bandwidth could up to 50GHz, but the disadvantage is that linewidth is just 15nm. To conquer this problem, we made another design, which is anomalous dispersion mirror. By AD mirror’s phase compensation, our PD’s linewidth could increase to 50nm. About process, we use SOI wafer to manufacture Germanium absorbed critical couple photodetector, which design for backside incident, can reach high frequency response and high bandwidth compare with traditional Si and Ge photodetectors.