Our 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.
It 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.
This 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.
This is a collection of the papers from the 7th International Workshop on Computational Electronics. They explore: semiconductor device modelling; optoelectronic device simulation; particle simulation methods; and nanostructures.
Physics and Modeling of Tera- and Nano-Devices is a compilation of papers by well-respected researchers working in the field of physics and modeling of novel electronic and optoelectronic devices. The topics covered include devices based on carbon nanotubes, generation and detection of terahertz radiation in semiconductor structures including terahertz plasma oscillations and instabilities, terahertz photomixing in semiconductor heterostructures, spin and microwave-induced phenomena in low-dimensional systems, and various computational aspects of device modeling. Researchers as well as graduate and postgraduate students working in this field will benefit from reading this book. Sample Chapter(s). Semiconductor Device Scaling: Physics, Transport, and the Role of Nanowires (784 KB). Contents: Semiconductor Device Scaling: Physics, Transport, and the Role of Nanowires (D K Ferry et al.); Polaronic Effects at the Field Effect Junctions for Unconventional Semiconductors (N Kirova); Cellular Monte Carlo Simulation of High Field Transport in Semiconductor Devices (S M Goodnick & M Saraniti); Nanoelectronic Device Simulation Based on the Wigner Function Formalism (H Kosina); Quantum Simulations of Dual Gate MOSFET Devices: Building and Deploying Community Nanotechnology Software Tools on nanoHUB.org (S Ahmed et al.); Positive Magneto-Resistance in a Point Contact: Possible Manifestation of Interactions (V T Renard et al.); Impact of Intrinsic Parameter Fluctuations in Nano-CMOS Devices on Circuits and Systems (S Roy et al.); HEMT-Based Nanometer Devices Toward Terahertz Era (E Sano & T Otsuji); Plasma Waves in Two-Dimensional Electron Systems and Their Applications (V Ryzhii et al.); Resonant Terahertz Detection Antenna Utilizing Plasma Oscillations in Lateral Schottky Diode (A Satou et al.); Terahertz Polarization Controller Based on Electronic Dispersion Control of 2D Plasmons (T Nishimura & T Otsuji); Higher-Order Plasmon Resonances in GaN-Based Field-Effect Transistor Arrays (V V Popov et al.); Ultra-Highly Sensitive Terahertz Detection Using Carbon-Nanotube Quantum Dots (Y Kawano et al.); Generation of Ultrashort Electron Bunches in Nanostructures by Femtosecond Laser Pulses (A Gladun et al.); Characterization of Voltage-Controlled Oscillator Using RTD Transmission Line (K Narahara et al.); Infrared Quantum-Dot Detectors with Diffusion-Limited Capture (N Vagidov et al.); Magnetoresistance in Fe/MgO/Fe Magentic Tunnel Junctions (N N Beleskii et al.); Modeling and Implementation of Spin-Based Quantum Computation (M E Hawley et al.); Quantum Engineering for Threat Reduction and Homeland Security (G P Berman et al.); Strong Phase Shift Mask Manufacturing Error Impact on the 65nm Poly Line Printability (N Belova). Readership: Academics, graduate and postgraduate students in the field of physics and modeling of novel electronics and optoelectronic devices.
Addressed to both students as a learning text and scientists/engineers as a reference, this book discusses the physics and applications of quantum-well infrared photodetectors (QWIPs). It is assumed that the reader has a basic background in quantum mechanics, solid-state physics, and semiconductor devices. To make this book as widely accessible as possible, the treatment and presentation of the materials is simple and straightforward. The topics for the book were chosen by the following criteria: they must be well-established and understood; and they should have been, or potentially will be, used in practical applications. The monograph discusses most aspects relevant for the field but omits, at the same time, detailed discussions of specialized topics such as the valence-band quantum wells.
Infrared technologies are very important for a wide range of military, scientific and commercial applications. Devices and systems based on semiconductor heterostructure and quantum well and quantum dot structures open up a new era in infrared technologies.This book deals with various topics related to the latest achievements in the development of intersubband infrared photodetectors, reviewed by top experts in the field. It covers physical aspects of the operation of the devices as well as details of their design in different applications. The papers included in the book will be useful for researchers and engineers interested in the physics of optoelectronic devices as well as their practical design and applications.
Herein, 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.
In the past, infrared imaging has been used exclusively for military applications. In fact, it can also be useful in a wide range of scientific and commercial applications. However, its wide spread use was impeded by the scarcity of the imaging systems and its high cost. Recently, there is an emerging infrared technology based on quantum well intersubband transition in III-V compound semiconductors. With the new technology, these impedances can be eliminated and a new era of infrared imaging is in sight. This book is designed to give a systematic description on the underlying physics of the new detectors and other issues related to infrared managing.
