Repeated radiation damage and thermal annealing of avalanche photodiodes

TL;DR

This study investigates the effectiveness of cyclical thermal annealing in maintaining low thermal noise in avalanche photodiodes subjected to simulated space radiation, ensuring their suitability for quantum communication satellites over extended missions.

Contribution

It demonstrates that repeated thermal annealing effectively controls thermal noise in APDs under simulated space radiation conditions, informing future space quantum communication device design.

Findings

Repeated annealing maintains thermal noise within acceptable limits for quantum key distribution.

Conditional annealing slightly outperforms fixed-interval annealing in end-of-life noise levels.

Afterpulsing probability increases with cumulative proton irradiation.

Abstract

Avalanche photodiodes (APDs) are well-suited for single-photon detection on quantum communication satellites as they are a mature technology with high detection efficiency without requiring cryogenic cooling. They are, however, prone to significantly increased thermal noise caused by in-orbit radiation damage. Previous work demonstrated that a one-time application of thermal annealing reduces radiation-damage-induced APD thermal noise. Here we examine the effect of cyclical proton irradiation and thermal annealing. We use an accelerated testing environment which emulates a realistic two-year operating profile of a satellite in low-Earth-orbit. We show that repeated thermal annealing is effective at maintaining thermal noise of silicon APDs within a range suitable for quantum key distribution throughout the nominal mission life, and beyond. We examine two strategies -- annealing at a fixed period of time, and annealing only when the thermal noise exceeds a pre-defined limit. We find both strategies exhibit similar thermal noise at end-of-life, with a slight overall advantage to annealing conditionally. We also observe that afterpulsing probability of the detector increases with cumulative proton irradiation. This knowledge helps guide design and tasking decisions for future space-borne quantum communication applications.