Ultra-broadband THz/IR upconversion and photovoltaic response in semiconductor ratchet-based upconverter

An ultra-broadband upconversion device is demonstrated by direct tandem integration of a p-type GaAs/AlxGa1-xAs ratchet photodetector (RP) with a GaAs double heterojunction light emitting diode (DH-LED) using the molecular beam epitaxy. An ultra-broadband photoresponse from the terahertz (THz) to near-infrared (NIR) region (4–200 THz) was realized, which covered a much wider frequency range compared with existing upconversion devices. Broadband IR/THz radiation from a 1000 K blackbody was upconverted into NIR light that could be detected via a commercial Si-based device. The normal incidence absorption of the RP simplified the structure of the RP-LED device and made it more compact than the intersubband transition-based upconverters. In addition to upconversion, the proposed upconverter was investigated as a photovoltaic detector in the infrared region (detection range from 18 to 150 THz) based on the ratchet effect without an applied bias voltage.