Enhancement of the infrared detection efficiency of silicon photon-counting avalanche photodiodes by use of silicon germanium absorbing layers

An enhancement of the infrared detection efficiency of Si photon-counting detectors by inclusion of SiGe absorbing layers has been demonstrated for what is believed to be the first time. An improvement of 30 times in detection efficiency at a wavelength of 1210 nm compared with that of an all-Si structure operated under identical conditions has been measured. The $\mathrm{Si}/{\mathrm{Si}}_{0.7}{\mathrm{Ge}}_{0.3}$ device is capable of room-temperature operation and has a response time of less than 300 ps.