Development of Voltage-Tunable IR Photodetector

Artificial Intelligence-based object recognition in the infrared spectrum region is essential for autonomous applications and will likely require on-demand spectral tuning of an imaging sensor. Here we develop a quantum well infrared photodetector (QWIP) with an asymmetrically doped double quantum well (QW) array which provides the means to control its spectral sensitivity with an applied bias. The test structures were designed using a Schrödinger-Poisson solver to find the electronic transition energies for symmetric and antisymmetric double-QW states. The design, growth, and characterization of QWIPs have been performed aiming at the 5-8 µm and 8-12 µm detection wavelengths. The structures were grown by molecular beam epitaxy and contained 25 periods of coupled double GaAs QWs and AlxGa1-xAs barriers. One of the QWs in the pair was doped to provide potential asymmetry allowing for control of the electron population on the split levels by the bias applied to the QWIP. The QW structures were calibrated using TEM, and tested with blackbody radiation and FTIR down to 77 K. As a result, the ratio of the responsivities of the two bands at about 8 and 11 µm as well as 5 and 8 µm was controlled with up to an order of magnitude by the applied bias within +/- 4V.