Near-unity excess noise factor of staircase avalanche photodiodes

If a receiver system is circuit-noise limited, avalanche photodiodes can be beneficial, as their internal gain mechanism can lead to a higher system signal-to-noise ratio. However, the extent of this benefit is intrinsically limited by the detectors' excess noise factor. The higher the factor, the lower the overall signal-to-noise ratio. The staircase avalanche photodiode proposed by Federico Capasso was designed to be a solid-state replacement for a photomultiplier tube in which discrete and deterministic gain would lead to a unity excess noise factor. The predicted gains for a staircase avalanche photodiode have recently been confirmed for one-, two-, and three-step structures [Nat. Photonics 15, 468 (2021)]. This paper presents measurements of the excess noise factor of two- and three-step staircase avalanche photodiodes. At an average gain of 4.01 and 7.24, the two- and three-step staircase avalanche photodiodes have an average excess noise factor of 1.02 and 1.08, respectively. (c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement