Design Of Single Photon Avalanche Diodes

Quantum information is a new technology by combination of quantum mechanics and information science, it is a great revolution to the classical information. For example, as an important part of quantum information, quantum computer have computing power that classical computer can’t go beyond. Also it will become a major threat to many existing encryption system. Beside that quantum cryptography provides an unconditional secure means of communication. After 20 years, development in quantum cryptography has moved from the laboratory gradually toward practical application.Single photon detector is a core device in many quantum information system. In quantum key distribution system, the performance of single photon detector can affect directly the performance of quantum key distribution system, including secret bit rate and the length over which secure keys can be distributed.In this thesis, we design two kinds of single photon detector:Silicon single photon diodes and InGaAs/InP single photon avalanche diodes. Silicon single photon avalanche photodiode has many applications in experimental test of fundamental problem in quantum mechanics, quantum cryptography, time resolved fluorescence spectrometer. According to length of the depletion layer, silicon single photon detector can be divided into thick and thin type avalanche photodiode. The thick type silicon avalanche photodiode have high detection efficiency, but it’s time resolution is poor. At the same time thin type silicon avalanche photodiode’s detection efficiency is not high enough, but it’s time resolution is very good. To solve this problem, we propose a novel silicon single photon avalanche photodiode. Different with the conventional silicon thin type silicon avalanche photodiode, there are nanostructure on the top of surface and bottom of diode. The depletion region is the same with thin type silicon single photon avalanche photodiode. By this way the detection efficiency of new silicon single photon avalanche photodiode have been improved a lot, the time resolution is still great because of thin depletion region. By optimizing the new structure silicon single photodiode we improve the detection efficiency further. We have designed a high detection efficiency avalanche photodiode that detection efficiency is even higher than the thick type silicon avalanche photodiode. Meanwhile because of its depletion region is much smaller, it have much better time resolution than the thick type silicon single photon avalanche photodiode.InGaAs/InP single photon avalanche photodiode have been used a lot in fiber quantum key distribution system. Detection efficiency, dark count, time resolution, after pulsing affect dramatically the secure rate and the distance over which the secure key can be distributed. In fifth chapter we investigate InGaAs/InP avalanche photodiode. In linear mode we introduce multiplication factor, the excess noise, response speed, and analyzes the factors that influence these parameter. In Geiger mode we analyze typical structure of InGaAs/InP avalanche photodiode, and calculate the electric field distribution inside the avalanche photodiode. Beside the electric field, we calculate the relationship between breakdown probability and excess bias, the breakdown probability distribution in the photodiode, and the temperature dependence of the breakdown voltage. Also we calculate the dark count rate of SPAD. These will provide some reference for the design of avalanche photodiode.