DC and noise characteristics of InP-based avalanche photodiodes for optical communication applications

The DC and low frequency noise characteristics of InGaAs/InP planar separate absorption, grading, charge, and multiplication (SAGCM) avalanche photodiode are reported. These devices have DC gains greater than 100 with about 0.3 μW input power and breakdown voltages V_br of 56 V. At 0.9 V_br, the dark current is typically 10 nA for a 30-μm-diameter active area device. The theoretical calculations of dark currents indicates that the primary dark currents come from generation-recombination and diffusion currents in both active and periphery regions. The breakdown voltage is in agreement with the calculation, which shows that the partial charge sheet does prevent the premature breakdown in the periphery region. The shot noise power is determined to be proportional to I^2.7, in agreement with theory. The lack of 1/f noise indicates the partial charge sheet is a good design to replace conventional guard ring design