Noise sources and their limitations on the performance of compound semiconductor hard radiation detectors

We report on the measurement of frequency dependent noise spectra of photoconductive ternary compounds Cs3Sb2I9, Rb3Sb2I9, Hg3Se2I2, and TlSn2I5 for hard radiation detectors. The major sources of noise in these detectors are attributed to pickup noise, white noise, and frequency related 1/f noise. At low frequencies, the noise spectral density function exhibited 1/f (alpha) behavior where alpha is less than or equal to one. For those samples with alpha equal to one, radiation detection performances of the detectors, in terms of spectral measurements, have been reported in previous publications. The origin of 1/f noise of those samples is attributed to carrier fluctuations associated with deep centers/trapped holes. For those samples with alpha less than one, the origin of the deviation from a linear 1/f dependence is unknown and currently under investigation. However, this deviation is correlated with higher background white noise and lowered detector performance, and thus indicates that the material needs to be further optimized. Noise measurements are a useful indicator for screening prospective materials and samples for detectors.