Research on high performance free-running mode InGaAs/InP NFAD readout circuit

In recent years, InGaAs/InP Negative Feedback Avalanche Diodes (NFAD), as a new type of high-sensitivity all-solid- state semiconductor device based on the structure of Single Photon Avalanche Diode (SPAD), integrates a quenching resistor on the SPAD chip. The quenching resistor is integrated on the SPAD chip, which is widely used in photon counting applications such as fluorescence spectrum detection, solar spectrum irradiation, quantum communication, and high-energy radiation monitoring due to its high integration, high sensitivity, fast quenching speed, low after-pulse, and high reliability. In the research, for the high-speed small-signal amplification and extraction, interference and noise suppression, and active-passive hybrid quenching of InGaAs/InP NFAD, a high-speed, low-noise, single-ended differential preamplifier circuit was innovatively used for the amplification and extraction of NFAD avalanche signals, and then a high-speed differential comparator was used for the identification and extraction of the avalanches, and they were quenched by the active-passive hybrid quenching branch, and recovered after a certain delay time. At the same time, the NFAD was reentered into the Geiger state by the recovery branch after a certain delay; meanwhile, the DAC chip containing 14-bit registers was used to realize the high-precision small-step (±1LSB) threshold voltage output to enhance the detector's anti-jamming ability, the input voltage V_DD of DAC was from 2.7V to 5.5V; the circuit can realize the fast quenching and recovery of the NFAD, with a bandwidth close to 1GHz, a quenching time of about 1.23ns, and a dead time of about 0.1μs to 100μs , which met the requirements of free-running-mode photon counting detection.