Terahertz range GaAs/AlGaAs quantum well photodetector

We have designed a GaAs/AlGaAs detector with a targeted peak frequency of 3 THz (100 mum) in an effort to extend the successful implementation of QWIP (Quantum Well Infrared Photodetector) arrays to the terahertz range. A simple multilayer structure has 18-nm GaAs QWs sandwiched between AlGaAs barriers with an Al alloy fraction of 2%. Despite the low Al content (2%), we obtained consistent results with MBE growth and could control the level of dark current and the impedance of fabricated devices within design-specific requirements. The level of dark current in optimized samples was a few muA/cm^-2 and the detector observed response close to the designed detection wavelength. The responsivity of the detector was measured with a calibrated blackbody source. A responsivity of 13 mA/W at an electric bias of 40 mV and an operating temperature of 4 K was obtained.