Avalanche photodiodes based on InAlAs/InGaAs heterostructures with sulfide–polyamide passivation of mesa structures

Subject of study. A method for the sulfide-polyamide surface passivation of mesa structures of InAlAs/InGaAs avalanche photodiodes was considered and the static properties of the fabricated crystals of InAlAs/InGaAs avalanche photodiodes were investigated. Aim of study. The study aimed to investigate the effect of sulfide-polyamide surface passivation of mesa structures on the principal parameters of an avalanche photodiode. Method. Sulfide-polyamide surface passivation of a mesa structure entails processing the surface in an aqueous solution of ammonium sulfide followed by the application of a protective layer of AD-9103-30 polyamide. Main results. Avalanche photodiodes based on InAlAs/InGaAs heterostructures were fabricated and investigated. The surface of the mesa structure of avalanche photodiodes underwent sulfide-polyamide passivation. Crystals of avalanche photodiodes with an active area diameter of 32 mu m reproducibly ensured a dark current of 10-20 nA under an applied voltage of 0.9 of the breakdown voltage, uniform distribution of the breakdown voltage value across the sample area, and the long-term stability of parameters. Spectral sensitivity values of the devices in the 1550 nm region were 0.85-0.88 A/W, and their capacitance values were 0.11-0.12 pF. Ensuring the reproducibility and long-term stability of parameters is crucial to passivation technology. Parameter measurements of the avalanche photodiode crystals with sulfide-polyamide passivation performed with a 6-month interval confirmed the temporal stability of the dark current at the level of 5%. Practical significance. The proposed method for the surface passivation of the mesa structure of InAlAs/InGaAs avalanche photodiodes entailing processing in an aqueous solution of ammonium sulfide followed by the application of a protective layer of AD-9103-30 polyamide can be used to fabricate avalanche photodiodes with a reproducible low level of dark current. (c) 2023 Optica Publishing Group