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Automated noise measurements for very long wavelength infrared detectors
KTH, School of Electrical Engineering and Computer Science (EECS).
2019 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

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.

Abstract [sv]

Bildkvaliteten hos bildgenererande infraröda (IR) detektorer påverkas av brusnivån i de enskilda pixlarna i detektormatrisen. Brusmätningar på pixelnivå kan därför ge en grundläggande förståelse för vad som begränsar detektorns prestanda. Noggranna studier av bruset, med mätningar vid olika spänningar och med hög frekvensupplösning kan dock vara väldigt tidskrävande, varför automatisering av dessa mätningar är nödvändigt.I detta examensarbete har automatisering av en brusmätuppställning för IR-detektorer utförts.Automatiseringen av brusmätsystemet har fungerat tillfredsställande och har använts för att mäta brus i olika sorters långvågiga IR-detektorer, såsom kvantbrunnsbaserade IR-detektorer (QWIP= Quantum well infrared photodetector) och typ-II supergitterbaserade IR-detektorer (T2SL = Type II superlattice).Resultaten av dessa studier har använts för att beräkna brusförstärkningsfaktorn i dessa detektorer. Studier av brusspektra från olika tillverkningsbatcher av QWIPar har varit en avgörande faktor för att förstå varför detektorprestanda varierar mellan olika batcher. För T2SL-baserade IRdetektorer har studier utförts för att avgöra inverkan av pixelformen, pixelstorlek och mörkerströmsnivå på brusnivån i dessa detektorer.

Place, publisher, year, edition, pages
2019. , p. 59
Series
TRITA-EECS-EX ; 2019:783
Keywords [en]
Noise, Infrared detector, QWIP, T2SL
Keywords [sv]
Brus, Infraröd detektor, QWIP, T2SL
National Category
Computer and Information Sciences
Identifiers
URN: urn:nbn:se:kth:diva-271186OAI: oai:DiVA.org:kth-271186DiVA, id: diva2:1415915
Subject / course
Engineering Physics
Examiners
Available from: 2020-03-20 Created: 2020-03-20 Last updated: 2020-03-20Bibliographically approved

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