1/f noise in Hg1-xCdxTe detectors

This paper investigates 1/f noise performance of Hg1-xCdxTe photovoltaic detectors when detector current is varied by changing detector area, bias, temperature and incident flux. Holding detector bias and temperature constant, measured 1/f noise current is proportional to the detector current. However for all detector areas measured, non-uniformity is observed in the noise current due to the varied quality of the detectors. Even for the lambda(c) = 16 mum, 4-mum-radius, diffusion-limited detectors at 78 K held at reverse bias, the average and standard deviation in dark current is Id = 9.76 +/- 1.59 x 10(-8) A while the average and standard deviation in noise current at 1 Hz in a 1 Hz bandwidth is in = 1.01 +/- 0.63 x 10(-12) A. For all detector areas measured at 100 mV reverse bias, the average and standard deviation in dark current to noise current ratio is alpha(D) = i(n) / I-d = 1.39 +/- 1.09 x 10(-5). Defects are presumed resident in the detectors that produce greater non-uniformity in the 1/f noise as compared to the dark current at 100 mV reverse bias. Noise was also measured as a function of temperature for two lambda(c) = 16 mum detectors from 55 K to 100 K. The average and standard deviation in the noise current to dark current ratio is OLD = i(n) / I-d = 2.36 +/- 0.83 x 10(-5) for the 26-mum-diameter detector and aD = i(n) / I-d = 1.71 +/- 0.69 x 10(-5) for the 16-mum-diameter detector. Dark and noise current were measured while changing the bias applied to a detector. In the diffusion-limited portion of the detector I-V curve, 1/f noise is independent of bias with alphaD = i(n) / Id = 1.51 +/- 0.12 x 10-5. When tunneling currents dominated, alpha(T) = i(n) / I-d = 5.21 +/- 0.83 x 10(-5). The 1/f noise associated with tunneling currents is a factor of three greater than the 1/f noise associated with diffusion currents. In addition, 1/f noise was measured on detectors held at -100 mV and 78 K under dark and illuminated conditions. The average noise to current ratio alpha(D) was approximately 1.5 x 10(-5) for dark and photon-induced diffusion current. However, detector-to-detector variations exist even within a single chip. The two most important points are that non-uniformities in material/fabrication need to be addressed and that each individual type of current component has an associated 1/f noise current component, the magnitude of the relationship being different depending on the source current.