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Extremely low excess noise and high sensitivity AlAs0.56Sb0.44 avalanche photodiodes


Fast, sensitive avalanche photodiodes (APDs) are required for applications such as high-speed data communications and light detection and ranging (LIDAR) systems. Unfortunately, the InP and InAlAs used as the gain material in these APDs have similar electron and hole impact ionization coefficients (α and β, respectively) at high electric fields, giving rise to relatively high excess noise and limiting their sensitivity and gain bandwidth product1. Here, we report extremely low excess noise in an AlAs0.56Sb0.44 lattice matched to InP. A deduced β/α ratio as low as 0.005 with an avalanche region of 1,550 nm is close to the theoretical minimum and is significantly smaller than that of silicon, with modelling suggesting that vertically illuminated APDs with a sensitivity of −25.7 dBm at a bit error rate of 1 × 10−12 at 25 Gb s−1 and 1,550 nm can be realized. These findings could yield a new breed of high-performance receivers for applications in networking and sensing.

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Fig. 1: Schematic of P1 and the measured multiplication results.
Fig. 2: Measured excess noise results.
Fig. 3: Optical sensitivity modelling.

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Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.


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D.L.H. acknowledges financial support provided by the Sêr Cymru National Research Network in Advanced Engineering and Materials. S.Y.X. acknowledges financial support from the European Regional Development Fund through the Welsh Government. B.L.L. acknowledges support from the National Science Foundation of the United States (ECCS-1810507).

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Authors and Affiliations



S.Y.X., B.L.L. and J.P.R.D. designed the structures. B.L.L., M.C.D. and D.L.H. carried out layer growth. L.W.L. conducted the device fabrication. X.Y. undertook the experimental measurements. J.S.C. and X.Y. undertook the absorption modelling. S.Y.X. performed the sensitivity simulations and SEM. X.Y., S.Y.X., C.H.T. and J.P.R.D. discussed and analysed the results, and wrote the manuscript. J.P.R.D., C.H.T. and D.L.H. supervised the project. All authors reviewed the manuscript and approved the paper.

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Correspondence to Shiyu Xie, Baolai Liang or John P. R. David.

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Fabrication process and noise measurements.

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Yi, X., Xie, S., Liang, B. et al. Extremely low excess noise and high sensitivity AlAs0.56Sb0.44 avalanche photodiodes. Nat. Photonics 13, 683–686 (2019).

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