Dual-epitaxy Si/Ge broadband photodetector for application in cryogenic radiometer

A dual-epitaxy Si/Ge broadband photodetector covering the wavelength range from 400 nm to 1600 nm was developed and demonstrated. The detector was realized on silicon platform with vertically stacked epitaxial Si and Ge layers in the detector's depletion region, which combined the response from a Si detector and a Ge detector. Under room temperature, dark current density of dual-epitaxy Si/Ge broadband photodetector is 1.3E-4 A/mm² at 2 V reverse bias. The dual-epitaxy Si/Ge broadband has its peak spectral responsivity response of more than 0.6 A/W near 1000 nm wavelength and has spectral responsivity above 0.1A/W in the range from 450 nm to 1600 nm. Its temperature dependency was studied. The dual-epitaxy Si/Ge quadrant detector was proved working in the application of absolution optical power measurement in cryogenic radiometer.