Terahertz frontside-illuminated quantum well photodetector

We have demonstrated the operation of a frontside-illuminated GaAs/AlGaAs quantum well photodetector based on intersubband absorption in a quantum well (QW) with a targeted peak frequency of 3 THz. A multiple quantum well structure consists of 20 periods of 18 nm QWs interleaved by 80 nm barriers with an Al alloy content of 2%. We measured the following performance characteristics: dark current, responsivity, and spectral response. A responsivity of 13 mA/W at an electric bias of 40 mV and an operating temperature of 3 K was obtained with a peak response close to the designed detection frequency. The dark current density was a few muA/cm² and was limited by thermally assisted tunneling through the barriers. We looked also at possible designs to optimize the devicepsilas performance.