Series resistance optimization of high-sensitivity si-based VUV photodiodes

Recently, silicon ultrashallow p
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n photodiodes, fabricated by a pure boron deposition technology (B-layer diodes), were evaluated for detection in the Vacuum Ultra-Violet (VUV) spectral range from 115 nm to 215 nm wavelengths, where the attenuation length in silicon is only a few nanometers. Superior sensitivity in the order of 0.1 A/W in the whole VUV spectral range was reported [1]. Next to the sensitivity, another important parameter of any photodetector is the response time, which is directly related to its series resistance. In this work a study of the relation between the sensitivity and the series resistance of the B-diodes is presented, supported by simulation results and optical/electrical experimental results. Moreover, practical methods for designing a high sensitivity VUV photodiodes while keeping a relatively low series resistance, are proposed. The experimental results demonstrate that by modifying the diode structure, the series resistance can be effectively reduced. At the same time, the B-layer diodes still maintain a high VUV sensitivity.