Experimental Determination of the Dependence Between Spectral Response and Current-Voltage Characteristics for MWIR HgCdTe Detectors

Experimental results are reported for a medium-wavelength infrared (MWIR) HgCdTe photodetector designed in a joint laboratory run by VIGO Photonics S.A. and the Military University of Technology. The parameters of the MWIR detectors fabricated with HgCdTe heterostructures were studied. Advances in the metal-organic chemical vapor deposition (MOCVD) technique enable the growth of HgCdTe epilayers with a wide range of composition and doping, used for uncooled infrared detectors. Device-quality HgCdTe heterostructures were deposited on 2-inch-diameter, low-cost (100) GaAs substrates. The heterostructures obtained were examined measuring the spectral response and current-voltage characteristics in different temperatures. Our intention here was to determine the relationship between electrical and optical results, using thermal analysis of dark current properties and photocurrent and spectral characteristics. The appearance of an additional signal source in certain ranges of reverse voltages was examined. Comparative analysis of the electrical and electro-optical characterization enabled us to isolate the photocurrent originating from different layers of the detector structure. Automated measurement techniques make it possible to correlate current responsivity with current-voltage curves measured as a function of temperature in a range from 10 K to 300 K with +/- 0.05 K resolution without human exertion. LabVIEW-aided data acquisition enables the averaging of each characteristic several hundred times, eliminates random and human errors, and decreases measurement uncertainty.