Automated noise measurements for very long wavelength infrared detectors

Abstract: The potential imaging performance of infrared (IR) detectors is dependent on the noise level in the detector pixels. Noise measurements at pixel level can therefore provide basic understanding of the intrinsic limitations of detectors. Accurate noise studies with measurements at different biases and with high frequency resolution can however consume a lot of time; therefore, automation of this process is necessary. In this thesis, automation of a noise measurement setup has been implemented. The noise measurement system that has been automated has proven to work for automatically acquiring noise spectra from long wavelength infrared detectors of different types, such as Quantum Well Infrared Photodetectors (QWIPs) and Type II-superlattice (T2SL) detectors. The results of these studies have been used to calculate the noise gain of the detectors. It also has been key to determine discrepancies between different QWIP fabrication batches and helped to clarify the differences in performance of the detectors from those batches. Regarding T2SL, noise measurements on detectors with big differences in dark current have been carried out. Finally, a study of the impact of pixel shape in T2sL noise has been conducted.