Silicon avalanche photodiodes with low multiplication noise and high-speed response

Low-noise and high-speed silicon avalanche photodiodes with low breakdown voltage are reported. The diode structure with a low-high-low impurity density profile is proposed to have low-noise characteristics. Multiplication noise and depletion layer width of several structures are compared theoretically, and effects of impurity density profile of the avalanche region are discussed. Built-in field is also provided to realize high-speed response without increasing operating voltage. Silicon avalanche photodiodes with the above mentioned structure have been fabricated with long time substrate annealing, ion implantation, and epitaxial growth. Attained performances are as follows: noise parameter k = 0.027 - 0.040, output pulse half width τ = 260 ps for a mode-locked Nd:YAG laser pulse, gain-bandwidth product up to 300 GHz at M = 400, quantum efficiency 0.55 - 0.66 at the 0.81- to 0.83-µm wavelength, and breakdown voltage about 100 V.