5 November 2013 Design of high sensitivity detector for underwater communication system
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Al0.52In0.48P is the largest bandgap material in III-V non-nitride semiconductors that is lattice matched to a readily available substrate (GaAs). Having a bandgap narrower than that of GaN enables it to detect wavelengths around 480 nm. Such wavelengths have the best transmittance underwater and may be used as a carrier in underwater communication systems. We present an Al0.52In0.48P homo-junction Separate-Absorption-Multiplication-Avalanche-Photodiode (SAMAPD) as a high sensitivity detector for such an application. By increasing the neutral and space-charge region thicknesses, the peak response wavelength can be tuned to longer wavelengths with a narrower full-width-half-maximum (FWHM). The quantum efficiency of the detector reduces with FWHM and this is compensated by having an avalanche gain. At room temperature, the SAM-APD has a dark current of <20 pA for a 210 μm radius device up to 99.9% of breakdown voltage. The structure gives a narrow spectral FWHM of 22 nm with centre wavelength of 482 nm. An external quantum efficiency of 33% and 6410% at 482 nm is obtained at bias voltage of -19 V and -92.6 V respectively.
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J. S. Cheong, J. S. Cheong, J. S. L. Ong, J. S. L. Ong, J. S. Ng, J. S. Ng, A. B. Krysa, A. B. Krysa, F. Bastiman, F. Bastiman, J. P. R. David, J. P. R. David, "Design of high sensitivity detector for underwater communication system", Proc. SPIE 8899, Emerging Technologies in Security and Defence; and Quantum Security II; and Unmanned Sensor Systems X, 88990G (5 November 2013); doi: 10.1117/12.2031953; https://doi.org/10.1117/12.2031953

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