An automated iterative nonlinear fitting program has been developed to model current-voltage (I-V) data measured on HgCdTe infrared (IR) detector diodes. This model includes the ideal diode diffusion, generation-recombination, bandto-band tunneling, trap-assisted tunneling (TAT), and avalanche breakdown as potential current limiting mechanisms in an IR detector diode. The modeling presented herein allows one to easily distinguish, and more importantly to quantitatively compare, the amount of influence each current limiting mechanism has on various detectors' I-V characteristics. Longer cutoff wavelength detectors often exhibit significant current limitations due to tunneling processes. The temperature dependence of these tunneling characteristics is thoroughly investigated for two diodes.

This article details current-voltage characteristics for a very long wavelength infrared (VLWIR) Hg 1ÿ x Cd x Te detector from Raytheon Vision Systems with a cutoff wavelength of 20.0 mm at 28 K. In this article, the VLWIR detector diode currents are modeled as a function of bias and temperature. This in-depth current model includes diffusion, band-to-band tunneling, trap-assisted tunneling (TAT), and shunt currents. The trap density has been extracted from the modeled TAT component of the current and was revealed to be relatively temperature-independent. An attempted incorporation of VLWIR detector susceptibility to stress has also been included through variation of the model parameter associated with the p-n junction electric field strength. This field variation accounts for stress induced piezoelectric fields. The current in this VLWIR detector was found to be diffusion-limited under much of the temperature and bias ranges analyzed. This modeling allows the scrutiny of both the dominant current-limiting mechanism and the magnitudes of the various current components as a function of both bias and temperature, allowing the straightforward determination of the ideal operating conditions for a given detector.

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