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DRS LPE-grown SWIR, MWIR and LWIR HgCdTe material are fabricated in the High-Density Vertically
Integrated Photodiode (HDVIP) architecture. Instruments manufactured for certain strategic applications have
severe constraints on excess low frequency noise due to the effect the noise has on the image quality with
subsequent consequences on the period of calibration. This paper will present data and analysis of excess low
frequency noise in LWIR (&lgr;c ~ 10.5 &mgr;m @ 60 K) HDVIP HgCdTe detectors.
The vehicle for noise measurements is a multiplexed 320 x 6 array of 40 &mgr;m x 50 &mgr;m, 10.5 &mgr;m cutoff, HgCdTe
detectors. Noise has been measured on a column of 320 detectors, at 60 K, as a function of frequency at zero and 50
mV reverse bias. Integration time for the measurement was 1.76 ms. Output voltage for the detectors was sampled
every 10th or every 100th frame. 32,768 frames of time series data were collected for a total record length of 98
minutes. Since the total time for collecting the 32,768 time data series points is 98 minutes, the minimum frequency
is 170 &mgr;Hz. Time series and Fourier transform data on individual detectors at 0 mV and 50 mV reverse bias in the
dark have been studied. Examination of the detector current time series and Fourier transform curves thereof, reveal
a variety of interesting characteristics: (i) time series displaying switching between four states characteristic of
random telegraph signal (RTS) noise, the noise current power spectrum having Lorentzian type characteristics; (ii)
time series data exhibiting slight wave-like characteristics with the noise current power spectrum being 1/f-like at
low frequencies; (iii) pronounced wave-like characteristics in the time series with the noise current power spectrum
being 1/f2-like at low frequencies; and (iv) time series having a mean value independent of time with the noise
current power spectrum being white. The predominance of detectors examined had minimal excess low frequency
noise down to ~ 10 mHz. In addition some isolated diodes had characteristics that lay between the four main types
outlined above.
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