Noise Characterization of HOT MWIR Interband Cascade Detectors

Interband Cascade (IC) infrared detectors utilizing type-II strained layer superlattice (T2SL) material show potential for high operating temperature (HOT) applications due in part to their ability to operate near zero bias with low dark current. The gain of IC detectors have been theorized to be inversely proportional to the number of stages of the devices wherein each stage contains an absorbing region, an interband relaxation region, and an interband tunneling region. As such, the shot-noise limited sensitivity is expected to be proportional to the square root of the number of stages hence allowing for higher sensitivity with an increased number of stages even as the external quantum efficiency is reduced. This presentation will contain analysis of experimentally attained dark current noise spectra of mid-wave infrared (MWIR) IC circular detectors with 100 – 400 μm diameters. The devices have 5 stages and were tested using a trans-impedance amplifier circuit with a cooled feedback resistor to limit amplifier noise. Data are presented for temperatures ranging from 120 K through 200 K and biases of – 500 mV through 100 mV. The results are compared to theoretical limits using the expected gain of the devices.