Thermal properties of mid-infrared colloidal quantum dot detectors

HgTe colloidal quantum dot films are studied for photodetection over the 3–5 μm atmospheric transparency window. The temperature dependence of the conductivity indicates that the material behaves approximately as an intrinsic semiconductor. In photoconduction, the responsivity can be as high as several hundred mA W^-1 at room temperature. The dark current presents 1/f noise which is larger than that for homogeneous conductors, and this noise decreases with temperature. A specific detectivity of 2 × 10⁹ Jones is obtained for a sample with a 6 μm cut-off wavelength at 130 K. These values are obtained for the thickest films studied (∼400 nm) and whose thicknesses are still much less than the optical absorption length. The time response can be faster than 100 ns.