Current-Voltage Analysis of Dual-Band n-p-n HgCdTe Detectors

We report an analysis of the current-voltage characteristics of a dual-band HgCdTe infrared detector built in an n-p-n configuration and designed for sequential mode operation in mid-wavelength (MW) and long-wavelength (LW) bands. The model treats the device as a pair of back-to-back p-n junctions and addresses both dark and illuminated conditions over a range of temperatures. We show that the assumption of ideal diode behavior (diffusion-only current) provides a very good first approximation, particularly at small bias voltages. We also find that a plot of the resistance-area product RA is the most sensitive indicator of the deviation from ideality, most of which is due to non-diffusion currents in the LW junction. We determine the apportionment of the applied voltage between the two junctions and show that for LW detection, less than half the total voltage appears across the reverse biased LW junction. Our approach should be useful in analyzing other dual-band test data and guiding design improvements. Graphical Abstract