The Effect of Contact Resistance on Short Wavelength Infrared Focal Plane Array Noise

Contact resistance can play a significant role in the noise performance of short wavelength infrared (SWIR) focal plane detector arrays (FPAs), particularly during cryogenic operation at low signal backgrounds. For astronomy FPAs, a source follower input cell ROIC is typically used in combination with correlated double sampling (CDS) or a form of up-the-ramp (SUTR) multi-sampling. In this paper, a pixel equivalent circuit model is presented and analyzed by standard techniques. The noise power density spectrum is analyzed for CDS and multi-sampled acquisitions, and it is found that there are three distinct ranges of contact resistance that govern excess noise behavior: the low-noise ROIC-limited range, the intermediate kTC-limited range, and the RC-bandwidth limited case. The model analyses are used to explain FPA data from Teledyne H2RG and H4RG SWIR FPAs. We have found that sampling sequence in combination with contact resistance can influence the total integrated noise, and can explain a FPA failure mode where anomalously low CDS and anomalously high SUTR noise exist in the same region.