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Engineering Semiconductor Nanostructures for Short-Wave Infrared Detection.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Engineering Semiconductor Nanostructures for Short-Wave Infrared Detection./
Author:	de Pina, Joao Martins.
Description:	1 online resource (171 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-09, Section: B.
Contained By:	Dissertations Abstracts International84-09B.
Subject:	Electrical engineering. -
Online resource:	click for full text (PQDT)
ISBN:	9798377618799

Engineering Semiconductor Nanostructures for Short-Wave Infrared Detection.
de Pina, Joao Martins.

Engineering Semiconductor Nanostructures for Short-Wave Infrared Detection. - 1 online resource (171 pages)

Source: Dissertations Abstracts International, Volume: 84-09, Section: B.

Thesis (Ph.D.)--University of Toronto (Canada), 2023.

Includes bibliographical references

Photodetectors fabricated using silicon and III-V compound semiconductors enable accurate light detection across the visible and infrared spectra. These, however, suffer from limited wavelength selectivity and from manufacturing costs that prohibit wider application.Solution-processed semiconductor nanostructures such as colloidal quantum dots (CQDs) represent a promising alternative. These combine ease of processing and a bandgap that is tunable across the short-wave infrared (SWIR) spectrum.At the outset of this study, CQD photodetectors sensitive to this spectral region suffered from high dark current (10-2 mA.cm-2), poor stability (a few hours), and low detection speed (fall time of 500 ns). In this thesis, I focus on the realization and investigation of new CQD device architectures and their effects on dark current, stability, and speed. I then explore the potential benefits of CQD photodetectors over epitaxial technologies.First I investigate the limitations of prior CQD photodetectors. I find that inadequate control over the band alignment and surface passivation lead to high dark current. I pursue the development of a surface-ligand engineering strategy that tailors the functionalities of each layer, enabling me to achieve record low dark current (10-3 mA.cm-2).Next, I study two performance-limiting factors: operating stability and speed. I examine a chief cause of photodetector instability - oxygen adsorption by the electron transport layer - and develop a synthesis method with 10x lower binding energy to oxygen. The new photodetectors are stable for over 100 hours. I then develop a device model to quantify the impact of charge transport layers on the detection speed and use this to fabricate 3x faster photodetectors (fall time of 150 ns).Finally, I explore the advantages of CQD photodetectors over traditional epitaxial semiconductors. I tune the spectral response of the CQDs to a SWIR band in which atmospheric absorption suppresses solar illumination. This results in CQD photodetectors achieving 140x higher signal-to-background ratio compared to Si-based photodetector systems. I then explore the integration of CQDs onto lattice-mismatched substrates, developing an interfacial layer that improves the injection of carriers into silicon.The studies herein offer routes to improve CQD photodetector performance and demonstrate the benefits of CQDs over epitaxial technologies.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798377618799Subjects--Topical Terms:

596380
Electrical engineering.
Subjects--Index Terms:

Colloidal quantum dotsIndex Terms--Genre/Form:

554714
Electronic books.

Engineering Semiconductor Nanostructures for Short-Wave Infrared Detection.
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520 $a Photodetectors fabricated using silicon and III-V compound semiconductors enable accurate light detection across the visible and infrared spectra. These, however, suffer from limited wavelength selectivity and from manufacturing costs that prohibit wider application.Solution-processed semiconductor nanostructures such as colloidal quantum dots (CQDs) represent a promising alternative. These combine ease of processing and a bandgap that is tunable across the short-wave infrared (SWIR) spectrum.At the outset of this study, CQD photodetectors sensitive to this spectral region suffered from high dark current (10-2 mA.cm-2), poor stability (a few hours), and low detection speed (fall time of 500 ns). In this thesis, I focus on the realization and investigation of new CQD device architectures and their effects on dark current, stability, and speed. I then explore the potential benefits of CQD photodetectors over epitaxial technologies.First I investigate the limitations of prior CQD photodetectors. I find that inadequate control over the band alignment and surface passivation lead to high dark current. I pursue the development of a surface-ligand engineering strategy that tailors the functionalities of each layer, enabling me to achieve record low dark current (10-3 mA.cm-2).Next, I study two performance-limiting factors: operating stability and speed. I examine a chief cause of photodetector instability - oxygen adsorption by the electron transport layer - and develop a synthesis method with 10x lower binding energy to oxygen. The new photodetectors are stable for over 100 hours. I then develop a device model to quantify the impact of charge transport layers on the detection speed and use this to fabricate 3x faster photodetectors (fall time of 150 ns).Finally, I explore the advantages of CQD photodetectors over traditional epitaxial semiconductors. I tune the spectral response of the CQDs to a SWIR band in which atmospheric absorption suppresses solar illumination. This results in CQD photodetectors achieving 140x higher signal-to-background ratio compared to Si-based photodetector systems. I then explore the integration of CQDs onto lattice-mismatched substrates, developing an interfacial layer that improves the injection of carriers into silicon.The studies herein offer routes to improve CQD photodetector performance and demonstrate the benefits of CQDs over epitaxial technologies.
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