High-power back-to-back dual-absorption germanium photodetector.

A high-power germanium photodetector is designed and fabricated using a cold-wall ultrahigh vacuum chemical vapor deposition. A back-to-back dual-absorption structure improves high-power characteristics by reducing the space-charge effect. Compared to a typical p-i-n photodetector, the saturated photocurrent of the back-to-back dual-absorption photodetector is improved from 16.2 to 21.3 mA at $ - {3}\;{\rm V}$-3V. At a bias voltage of $ - {1}\;{\rm V}$-1V, the dark current is 1.31 µA. The optical responsivities are 0.31 and 0.52 A/W at 1550 and 1310 nm, respectively. The 3 dB bandwidth of 4.14 GHz is achieved at $ - {3}\;{\rm V}$-3V. Theoretically, the 3 dB bandwidth can be further optimized in future device fabrication.