Scientists have created an IR detector with two separate IR bands and a bias-switchable spectral response. On reversing the detector’s bias voltage, the gadget changes from the near-infrared (NIR) to the shortwave infrared (SWIR) band. It is possible to integrate the silicon-based dual-band photodetector into existing camera circuits and cellphones.
A thin layer of Si acts as the detector’s foundation; layers of germanium (Ge) and germanium-tin (GeSn) semiconductor materials are placed on top of the Si layer, forming a vertical GeSn/Ge/Si stack grown epitaxially on a Si wafer. The combination of Si, Ge, and Sn expands the IR detector’s spectrum range of operation while also leveraging Si technology.
Simply by changing the bias polarity, the spectral response of the dual-band GeSn/Ge/Si detector can change in the wavelength range between 1.05 and 2.45 μm (NIR-SWIR). At the pixel level, the IR detector allows voltage-tunable operation over these two optical bands. In different IR bands of the spectrum, each pixel can capture the same image. The ability to flip between NIR and SWIR under identical illumination conditions allows access to data that is not available from just one wavelength band.