Colloidal Quantum Dot Schottky Barrier Photodetectors
Author: Jason Paul Clifford
Publisher:
Published:
Total Pages:
ISBN-13:
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Colloidal Quantum Dot Schottky Barrier Photodiodes
Author: Jason Paul Clifford
Publisher:
Published: 2008
Total Pages: 398
ISBN-13: 9780494579725
DOWNLOAD EBOOKHerein, we report the first solution-processed broadband photodetectors to break the past compromise between sensitivity and speed of response. Specifically, we report photodiodes having normalized detectivity (D*) > 1012 Jones and a 3dB bandwidth of > 2.9 MHz. This finding represents a 170,000 fold improvement in response speed over the most sensitive colloidal quantum dot (CQD) photodetector reported1 and a 100,000 fold improvement in sensitivity over the fastest CQD photodetector reported2.Efficient, sensitive semiconductor photodiodes are based on two fundamental characteristics: a large built-in potential that separates photogenerated charge carriers and minimizes internal noise generation, and high semiconductor conductivity for efficient collection of photogenerated charge. Schottky barriers to CQD films were developed to provide high, uniform built-in potentials. A multi-step CQD ligand exchange procedure was developed to allow deposition of tightly packed films of CQDs with high mobility and sufficiently well-passivated surfaces to form high-quality metallurgical junctions.The temporal response of the CQD photodiodes showed separate drift and diffusion components. Combined with detailed measurements of the Schottky barrier, these characteristics provided the physical basis for a numerical model of device operation. Based on this understanding, devices that excluded the slow diffusive component were fabricated, exploiting only the sub-microsecond field-driven transient to achieve MHz response bandwidth.At the outset of this study, sensitive, solution-processed IR photodetectors were severely limited by low response speeds1. Much faster response speeds had been demonstrated by solution-processed photodetectors operating in the visible3, but these devices offered no benefits for extending the spectral sensitivity of silicon. No available solution-processed photodetector combined high sensitivity, high operating speed, and response to illumination across the UV, visible and IR.We developed a fast, sensitive, solution-processed photodetector based on a photodiode formed by a Schottky barrier to a CQD film. Previous attempts to form sensitive photodetectors based on CQD photodiodes had demonstrated low quantum efficiencies that limited sensitivity4,5.These devices are the first to combine megahertz-bandwidth, high sensitivity, and spectral-tunability in photodetectors based on semiconducting CQDs. Record performance is achieved through advances in materials and device architecture based on a detailed understanding the physical mechanisms underlying the operation of CQD photodiodes.
Quantum Dot Photodetectors
Author: Xin Tong
Publisher: Springer Nature
Published: 2021-09-17
Total Pages: 319
ISBN-13: 3030742709
DOWNLOAD EBOOKThis book presents a comprehensive overview of state-of-the-art quantum dot photodetectors, including device fabrication technologies, optical engineering/manipulation strategies, and emerging photodetectors with building blocks of novel quantum dots (e.g. perovskite) as well as their hybrid structured (e.g. 0D/2D) materials. Semiconductor quantum dots have attracted much attention due to their unique quantum confinement effect, which allows for the facile tuning of optical properties that are promising for next-generation optoelectronic applications. Among these remarkable properties are large absorption coefficient, high photosensitivity, and tunable optical spectrum from ultraviolet/visible to infrared region, all of which are very attractive and favorable for photodetection applications. The book covers both fundamental and frontier research in order to stimulate readers' interests in developing novel ideas for semiconductor photodetectors at the center of future developments in materials science, nanofabrication technology and device commercialization. The book provides a knowledge sharing platform and can be used as a reference for researchers working in the fields of photonics, materials science, and nanodevices.
Light Emitting Diodes And Photodetectors Based On Iii-nitride And Colloidal Quantum Dot Materials
Author: Zhenyu Jiang
Publisher:
Published: 2014
Total Pages:
ISBN-13:
DOWNLOAD EBOOKIn this work, we first proposed the tandem architecture for solution-processed near infrared PbSe colloidal quantum dot (CQD)-based photodetectors to address the high dark current issue. The tandem architecture not only absorbs the virtue of tandem solar cell by means of efficient photon-to-current conversion, but also functions as the effective barrier that can block the leakage current. More than three orders of magnitude reduction in dark current has been observed, along with an elevated photocurrent. The low temperature current-voltage characteristics revealed that the tandem architecture posed a high energy barrier which effectively blocks the dark current. Our results suggest that tandem architecture can be employed to developing high-performance solution-processed photodetector. The application of tandem photodetectors was further extended to sensors on flexible substrates where little study has been reported to date. Our results on flexible tandem photodetectors validate the high efficiency and detectivity of the tandem architecture. Two different bending states have been studied which revealed the small critical bend radii of ~8mm and ~3mm for tensile and compressive bending, respectively. The photodetector performance remains stable under mechanical stress which offers great potential of CQDs-based tandem photodetectors for flexible device applications. Furthermore, we have demonstrated the chip level integration of flip-chip light emitting diode (LED) with current rectifying GaN Schottky barrier diodes constituting the Wheatstone bridge circuitry for alternating current (AC) driving. The flip-chip LED scheme offers better p-contact, high light extraction efficiency and fast heat dissipation. The reflectance and turn-on voltage were investigated under various p-contact annealing conditions. The flip-chip alternating current LEDs (ACLEDs) demonstrated more than ~23% improvement in terms of energy conversion efficiency over top-emissive ACLEDs and offer the potential of using such device for high brightness, high power, high efficiency and high reliability solid state lighting applications. Finally, built on our studies of LEDs and photodetectors, and of chip level integration of LEDs and GaN Schottky barrier diodes. we, for the first time, proposed the integration of visible LEDs and UV GaN photodetectors for bi-directional optical wireless communication (OWC) applications. The LEDs function as transmitters to emit visible light signal whereas the photodetectors as receivers to collect UV signals. The crosstalk can be neglected due to the superior visible-blind property of GaN UV photodetector. The experimental results demonstrated that the LEDs and photodetectors can work together efficiently which opens up a new avenue for using such device for bi-directional OWC applications.
Colloidal Quantum Dot Optoelectronics and Photovoltaics
Author: Gerasimos Konstantatos
Publisher: Cambridge University Press
Published: 2013-11-07
Total Pages: 329
ISBN-13: 0521198267
DOWNLOAD EBOOKCaptures the most up-to-date research in the field, written in an accessible style by the world's leading experts.
Flexible Colloidal Quantum Dot Photodetection with Cellulose Structures
Author: Jingda Wu
Publisher:
Published: 2016
Total Pages: 82
ISBN-13:
DOWNLOAD EBOOKThis thesis will outline a new way of fabricating flexible photodetectors. Solution-processable colloidal quantum dots (QDs, or nanocrystals(NCs)) are incorporated into cellulose structures to form a composite structure that can be used for photodetection. This enables new ways of device fabrication and also makes ultrathin, ultraflexible and even transparent optoelectronic devices possible. Inkjet printing with an office inkjet printer is introduced and applied towards PEDOT:PSS transparent electrode deposition. This offers a low cost method for material deposition. Flexible photoconductors are fabricated with these electrodes and CdSe quantum dot embedded tracing paper by utilizing the porous cellulose structure. Consistent photoresponse is achieved with such a structure under 550nm light illumination. After further realizing the shortcomings of tracing paper for its large thickness and low porosity, which both deteriorate the performance of these devices, natural plant-membranes are chosen as an alternative and offer superb properties for optoelectronic device fabrication. Visible-blind self-powered ultra-violet detectors are designed and fabricated with the incorporation of ZnO NCs on reed membrane. Schottky junction devices are fabricated with the use of gold and aluminum as the electrodes. Sub-second responses are observed at a bias of zero, which is superior than most of the flexible photoconductors in the literature. An external quantum efficiency of over 3% is discovered with the device at 350nm light illumination under zero bias. A great performance enhancement is also observed on the devices fabricated on reed membrane comparing to the ones on tracing paper. Nanofibrillated cellulose(NFC) can be readily used to fabricate transparent papers. ZnO NC-NFC composite structure is prepared and fabricated into ultrathin transparent papers with a thickness less than 1 micrometer. Self-powered Schottky photodiodes are fabricated on such papers and relatively fast response is observed at zero bias.
Quaternary Capped In(Ga)As/GaAs Quantum Dot Infrared Photodetectors
Author: Sourav Adhikary
Publisher: Springer
Published: 2017-09-06
Total Pages: 72
ISBN-13: 9811052905
DOWNLOAD EBOOKThis book introduces some alternative methods for enhancing the performance of In(Ga)As/GaAs-based quantum dot infrared photodetectors (QDIPs). In(Ga)As/GaAs-based QDIPs and focal plane array (FPA) cameras have wide application in fields such as military and space science. The core of the study uses a combination of quaternary In0.21Al0.21Ga0.58As and GaAs spacer as a capping layer on In(Ga)As/GaAs quantum dots in the active region of the detector structure. For the purposes of optimization, three types of samples growths are considered with different capping thicknesses. The results presented include TEM, XRD and photoluminescence studies that compare combination barrier thickness and its effect on structural and optical properties. Compressive strain within the heterostructure, thermal stability in high temperature annealing, spectral response, shifts in PL peaks peak,and responsivity and detectivity are all considered. The results also present a narrow spectral width that was obtained by using InAs QDs which is very useful for third generation FPA camera application. The book details effect of post-growth rapid thermal annealing on device characteristics and methods to enhance responsivity and peak detectivity. The contents of this book will be useful to researchers and professionals alike.
Quantum Dot Infrared Photodetectors Based on Structures with Potential Barriers
Author: Li-Hsin Chien
Publisher:
Published: 2011
Total Pages: 112
ISBN-13:
DOWNLOAD EBOOKIt is known that major restrictions of room-temperature semiconductor photodetectors and some other optoelectronic devices are caused by short photoelectron lifetime, which strongly reduces the photoresponse. Detectors based on nanostructures with potential barriers have the strong potential to overcome the limitations in quantum well photodetectors due to various possibilities for engineering of specific kinetic and transport properties. Here I review photocarrier kinetics in traditional quantum dot infrared photodetectors and present results of the investigations related to the quantum-dot (QD) structures with potential barriers created around dots and with collective barriers surrounding groups of quantum dots (planes, clusters etc). To optimize the photodetectors based on QD structures, I develop and exploit a model of the room-temperature QD photodetector. Using Monte-Carlo simulations, I investigate photoelectron capture and transit processes, as functions of selective doping of a QD structure, its geometry, and applied electric field. The simulation results demonstrate that the capture processes are substantially suppressed by the collective potential barriers around the groups of QDs. Detailed analysis shows that the effects of the electric field can be explained by electron heating, i.e. field effects become significant, when the shift of the electron temperature due to electron heating reaches the barrier height. Besides manageable photoelectron kinetics, which allows one to employ QDIP as an adaptive detector with changing parameters, the advanced QD structures will also provide high coupling to radiation, low generation-recombination noise, and high scalability.
Sensitive Quantum-Dot Infrared Photodetector with Barrier-Limited Photoelectron Capture
Author:
Publisher:
Published: 2002
Total Pages: 5
ISBN-13:
DOWNLOAD EBOOKOur research on quantum-dot infrared photodetectors has been concentrated on increasing of photoconductive gain and responsivity. Innovative idea in design of sensitive quantum-dot infrared photodetector is to use a structure with quantum dots surrounded by repulsive potential barriers, which are created due to interdot doping. Spatial separation of the localized ground state and continuum conducting states of the electron increases significantly the photoelectron capture time and photoconductive gain. Large value of the gain results in high responsivity, which in turn improves detectivity and raises the device operating temperature.
Quantum Dot Devices
Author: Zhiming M. Wang
Publisher: Springer Science & Business Media
Published: 2012-05-24
Total Pages: 375
ISBN-13: 1461435706
DOWNLOAD EBOOKQuantum dots as nanomaterials have been extensively investigated in the past several decades from growth to characterization to applications. As the basis of future developments in the field, this book collects a series of state-of-the-art chapters on the current status of quantum dot devices and how these devices take advantage of quantum features. Written by 56 leading experts from 14 countries, the chapters cover numerous quantum dot applications, including lasers, LEDs, detectors, amplifiers, switches, transistors, and solar cells. Quantum Dot Devices is appropriate for researchers of all levels of experience with an interest in epitaxial and/or colloidal quantum dots. It provides the beginner with the necessary overview of this exciting field and those more experienced with a comprehensive reference source.
