Voltage-tunable dual-band Ge/Si photodetector operating in VIS and NIR spectral range

Extending and controlling the spectral range of light detectors is very appealing for several sensing and imaging applications.Here we report on a normal incidence dual band photodetector operating in the visible and near infrared with a bias tunable spectral response.The device architecture is a germanium on silicon epitaxial structure made of two back-toback connected photodiodes.The photodetectors show a broad photoresponse extending from 390nm to 1600nm with the capability to electronically select the shorter (400-1100 nm) or the longer (1000-1600 nm) portion with a relatively low applied voltage.Devices exhibit peak VIS and NIR responsivities of 0.33 and 0.63 A/W, respectively, a low optical crosstalk (<-30dB), a wide dynamic range (>120dB) and, thanks to their low voltage operation, maximum specific detectivities of 7•10 11 cmHz 1/2 /W and 2•10 10 cmHz 1/2 /W in the VIS and NIR, respectively.