Quantum Dot Infrared Photodetectors Research Articles

A HIGH OPERATING TEMPERATURE (HOT) MIDDLE WAVE INFRARED (MWIR) QUANTUM-DOT PHOTODETECTOR

In this paper, a high operating temperature (HOT) middle wave infrared (MWIR) InAs/GaAs quantum dot (QD) infrared photodetector (QDIP) is reported. The QDIP covers a wide detection spectrum range from 3 μm to 6 μm. A large photoresponsivity of 6.4 A/W at a low bias voltage of 0.5 V and a high peak specific photodetectivity D* of 6.0 × 107cmHz1/2/W were obtained at a high operating temperature of 230 K.

The influence of background As on GaSb/GaAs quantum dots and its application in infrared photodetectors

AbstractIn this paper, GaSb nanostructures prepared under different Sb/background As ratios are investigated. With decreasing Sb/background As ratios, the morphologies of GaSb nanostructure changing from quantum dots (QDs) to quantum rings (QRs) are observed. The higher optical recombination probabilities of GaSb QRs are attributed to enhanced electron‐hole wave function overlapping and more surrounding electrons around the GaSb QR core shell. With well‐control Sb/background As ratios, the high‐temperature operation GaSb quantum‐dot infrared photodetector (QDIP) with simple stacked structure has been demonstrated. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

High-performance, long-wave (∼10.2 μm) InGaAs/GaAs quantum dot infrared photodetector with quaternary In0.21Al0.21Ga0.58As capping

A high-performance InGaAs/GaAs vertical quantum dot infrared photodetector (QDIP) with combined barrier of quaternary In0.21Al0.21Ga0.58As and GaAs was investigated in this study. A dominant long wavelength (∼10.2 μm) response was observed from the device. The device demonstrates large responsivity (2.16 A/W) with narrow spectral-width (Δλ/λ ∼0.14) and high detectivity (1.01 × 1011 cm Hz1/2/W at 0.3 V) at 10.2 μm at 77 K. In addition, the device has also produced a detectivity in the order of 6.4 × 1010 cm Hz1/2/W at 100 K at a bias of 0.2 V, indicating its suitability for high-temperature operations.

A numerical approach for analyzing quantum dot infrared photodetectors' parameters

Quantum dot infrared photodetectors (QDIPs) have many advantages over other types of semiconductor-based photodetectors. However some of its characteristics have been investigated theoretically, there are many unstudied points. In this paper a new approach is presented to evaluate quantum dot infrared photodetectors dark current and photocurrent. In this study, it is assumed that both thermionic emission and field-assisted tunneling mechanisms determine the dark current of quantum dot detectors. Based on these assumptions, new formula for average number of electron in a quantum dot for both, dark and illumination condition is calculated, which is more accurate than the previous reported formulas; because in deriving previous reported formulas, it was assumed only thermionic emission determines dark current but field-assisted tunneling mechanisms has not been considered. Then numerical method is used to calculate the average number of electron in a quantum dot and to determine dark current and photocurrent. The theoretical results are compared with experimental data. They have good agreement with available experimental data.

Block diagram modeling of quantum dot infrared photodetectors

The main objective of this paper is to evaluate the performance of quantum dot infrared photodetectors (QDIPs). The tools that we are used are the VisSim environment, along with the block diagram programming procedures. The benefits of using this modeling language are the simplicity of carrying out the performance's measurement through computer simulation instead of setting up a practical procedure which becomes expensive, as well as the difficulty of its management. The roles that the parameters of fabrication can play in the characteristics of QDIPs are discussed through developed models implemented by VisSim environment. VisSim can be a powerful supplement to model the Poisson equation. MAPLE software is used to devise this model. The theoretical result confirms that implicit solution of QDIPs governed by dynamic equations provides exact handling of the device performance. As an example, dark current, photocurrent, and detectivity are investigated. In order to confirm our models and their validity on the practical applications, we make a comparison between the results obtained by MAPLE, VisSim, and that experimentally published, and full agreement is observed. The implemented models can help designers and scientists optimize their devices to meet their requirements.

III-Nitride-Based Quantum Dots and Their Optoelectronic Applications

Abstract During the last two decades, III-nitride-based quantum dots (QDs) have attracted great attentions for optoelectronic applications due to their unique electronic properties. In this paper, we first present an overview on the techniques of fabrication for III-nitride-based QDs. Then various optoelectronic devices such as QD lasers, QD light-emitting diodes (LEDs), QD infrared photodetectors (QDIPs) and QD intermediate band (QDIB) solar cells (SCs) are discussed. Finally, we focus on the future research directions and how the challenges can be overcome.

Electrical characterization of Ni/Au/AuGe contacts for quantum dot infrared photodetectors

Transfer length method (TLM) structures were fabricated to characterize the Ni/Au/AuGe–n +–GaAs contacts for quantum dot infrared photodetector (QDIP). Low specific contact resistance of the order of 10 −5 Ω cm 2 indicates formation of a good Ohmic contact. The current–voltage measurements show that current transport is linear with no significant interfacial modification due to alloying of the contact metal. Low contact resistance makes this scheme suitable for the fabrication of heterostructure QDIP devices.

Plasmonic-Enhanced Photodetectors for Focal Plane Arrays

Plasmonic enhancement of a quantum-dot infrared photodetector (QDIP) using a corrugated metal surface (CMS) that is fully compatible with conventional focal plane array manufacturing is demonstrated. A CMS consisting of a 2.5-μm period, 2-D square array of 1.1-μ m-high GaAs circular posts passivated with a thick Au film is fabricated into the heavily doped, top GaAs contact layer of an InAs QDIP. For substrate-side illumination, the CMS exhibits strong coupling to surface plasma waves bound to the Au/GaAs interface providing enhancement of the QDIP. At 77 K, the CMS-processed QDIP exhibits up to ~15-fold detectivity enhancement compared with the original detector.

Detectivity Performance of Quantum Wire Infrared Photodetectors

Abstract The manuscript is devoted to calculate the detectivity, Figure of merit, of the quantum wire infrared photodetectors (QRIPs). The importance arises from two points. Firstly, the QRIPs give a stable and controllable performance in comparison with quantum dot infrared photodetectors (QDIPs). Secondly, the gap; difference between the photo and dark currents, is high enough to obtain a distinguished responsivity and detectivity. So, the dependence of detectivity behavior on the QRIPs parameters is discussed. From the results, one can notice that the superiority of QRIPs over the QDIPs which gives higher values of detectivity, about ten times or higher the latter under the same conditions. Hence, an improvement of the responsivity and detectivity of QRIPs compared to QDIPs has been perceived.

Investigation for optoelectronic characteristics and imaging performance of InAs quantum dot covered with In<sub>0.1</sub>Ga<sub>0.9</sub>As/GaAs multilayer based focal plane array

We report on a structure prepared by metalorganic chemical vapor deposition and molecular beam epitaxy techniques incorporated with a standard process of compound semiconductor to achieve In0.1Ga0.9As/InAs/In0.1Ga0.9As quantum dot infrared photodetector (QDIP)-based focal plane array. For investigating the mechanism of carrier transport and optoelectronic behavior, the photoresponse spectra and dark current were measured in agreement with the theoretical simulations. Furthermore, a model is proposed with the systematic analyses and explained for designing high-performance QDIPs based on the calculations of thermal activation energy and detectivity. For QDIP photoresponse measurements, the photovoltaic photoresponse is achieved, which can be attributed to the asymmetric morphology of quantum dot epitaxy. With increasing bias, the photoresponse spectra exhibit a redshift due to band bending that generates a thinner triangle barrier which increases the escape possibility of the excited carriers situated at lower excited-state levels. The trapezoid-edged scheme enhances infrared coupling and increases the photoresponse intensity. A single-sided gradient AlxGa1-xAs (x = 0.25→0) barrier can suppress the dark-current under bias efficiently. The infrared imaging performance of InGaAs QDIP based on 320×256 FPA is also demonstrated in this paper.

Noise, Gain, and Responsivity in Low-Strain Quantum Dot Infrared Photodetectors With up to 80 Dot-in-a-Well Periods

We present a systematic study of noise, gain, responsivity, and specific detectivity D* , in a series of low-strain dot-in-a-well (DWELL) quantum dot infrared photodetectors (QDIPs). The lattice-matched GaAs quantum wells and AlGaAs barriers in these devices prevent the accumulation of excessive strain and allow the growth of up to 80 DWELL periods. We show that the photoconductive gain in these QDIPs is inversely proportional to the number of periods, while the total quantum efficiency is proportional to the number of periods, meaning that the responsivity remains constant at a given mean electric field as the number of periods is varied. The dark current in each QDIP was also found to be constant at a given mean electric field.

Two-color In0.4Ga0.6As/Al0.1Ga0.9As quantum dot infrared photodetector with double tunneling barriers

We report a two-color quantum dot infrared photodetector (QDIP) using double tunneling barriers (DTBs) on one side of the InGaAs/AlGaAs dots. The two-color detection is achieved by changing the polarity of the applied bias voltages. In contrast, the same QDIP structure without the DTBs does not exhibit this detection wavelength tunability by switching the bias polarity. The two-color detection is ascribed to a different escape mechanism of electrons between positive and negative biases. The electrons escape out of the quantum well through resonant tunneling for a positive bias voltage while tunnel through a triangular barrier for a negative bias voltage.

An intermediate-band-assisted avalanche multiplication in InAs/InGaAs quantum dots-in-well infrared photodetector

The avalanche multiplication of photocurrent in InAs/InGaAs quantum dot infrared photodetectors (QDIPs) has been observed in the temperature range from 20 to 80 K. The avalanche onset voltage Vth, being larger than 1.2 V at T<55 K, is reduced to less than 0.8 V at T>60 K. This singularity of Vth indicates that intermediate-band-assisted avalanche multiplication is achieved in our dots-in-well structure, which benefits from the abrupt change of the electron occupation of the intermediate band at a temperature of approximately 55 K. The remarkable reduction of Vth for QDIP is a useful enhancement in the infrared detector’s performance.

Investigation of the quantum dot infrared photodetectors dark current

Quantum dot infrared photodetectors (QDIPs) are more efficient than other types of semiconductor based photodetectors; so it has become an actively developed field of research. In this paper quantum dot infrared photodetector dark current is evaluated theoretically. This evaluation is based on the model that was developed by Ryzhii et al. Here it is assumed that both thermionic emission and field-assisted tunneling mechanisms determine the dark current of QDIPs; moreover we have considered Richardson effect, which has not been taken into account in previous research. Then a new formula for estimating average number of electrons in a quantum dot infrared photodetector is derived. Considering the Richardson effect and field-assisted tunneling mechanisms in the dark current improves the accuracy of algorithm and causes the theoretical data to fit better in the experiment. The QDIPs dark current temperature and biasing voltage dependency, contribution of thermionic emission and field-assisted tunneling at various temperatures and biasing voltage in the QDIPs dark current are investigated. Moreover, the other parameter effects like quantum dot (QD) density and QD size effect on the QDIPs dark current are investigated.

Versatile Spectral Imaging With an Algorithm-Based Spectrometer Using Highly Tuneable Quantum Dot Infrared Photodetectors

We report on the implementation of an algorithm-based spectrometer capable of reconstructing the spectral shape of materials in the mid-wave infrared (MWIR) and long-wave infrared (LWIR) wavelengths using only experimental photocurrent measurements from quantum dot infrared photodetectors (QDIPs). The theory and implementation of the algorithm will be described, followed by an investigation into this algorithmic spectrometer's performance. Compared to the QDIPs utilized in an earlier implementation, the ones used here have highly varying spectral shapes and four spectral peaks across the MWIR and LWIR wavelengths. It has been found that the spectrometer is capable of reconstructing broad spectral features of a range of bandpass infrared filters between wavelengths of 4 and 12 as well as identifying absorption features as narrow as 0.3 in the IR spectrum of a polyethylene sheet.

Comparison studies of infrared photodetectors with a quantum-dot and a quantum-wire base

AbstractThis paper mainly presents a theoretical analysis for the characteristics of quantum dot infrared photodetectors (QDIPs) and quantum wire infrared photodetectors (QRIPs). The paper introduces a unique mathematical model of solving Poisson’s equations with the usage of Lambert W functions for infrared detectors’ structures based on quantum effects. Even though QRIPs and QDIPs have been the subject of extensive researches and development during the past decade, it is still essential to implement theoretical models allowing to estimate the ultimate performance of those detectors such as photocurrent and its figure-of-merit detectivity vs. various parameter conditions such as applied voltage, number of quantum wire layers, quantum dot layers, lateral characteristic size, doping density, operation temperature, and structural parameters of the quantum dots (QDs), and quantum wires (QRs). A comparison is made between the computed results of the implemented models and fine agreements are observed. It is concluded from the obtained results that the total detectivity of QDIPs can be significantly lower than that in the QRIPs and main features of the QRIPs such as large gap between the induced photocurrent and dark current of QRIP which allows for overcoming the problems in the QDIPs. This confirms what is evaluated before in the literature. It is evident that by increasing the QD/QR absorption volume in QDIPs/QRIPs as well as by separating the dark current and photocurrents, the specific detectivity can be improved and consequently the devices can operate at higher temperatures. It is an interesting result and it may be benefit to the development of QDIP and QRIP for infrared sensing applications.

High-Temperature Operation GaSb/GaAs Quantum-Dot Infrared Photodetectors

A ten-period GaSb/GaAs quantum-dot infrared photodetector (QDIP) is investigated in this letter. A broad detection window 2-5 μm with peak responses at ~ 3.7 μm is observed. Compared with the 4- to 8-μm detection window of a standard InAs/GaAs QDIP, the detection wavelengths of the GaSb/GaAs QDIP are shifted to the 2- to 5- μm range such that water absorption is avoided. The enhanced normal incident absorption of the GaSb QDIP is attributed to its smaller sizes compared with InAs QDs. Without additional high-bandgap barrier layers, the 200 K spectral response of the simple stacked GaSb/GaAs QDIP has already been observed, which has demonstrated the potential for practical applications of the GaSb/GaAs QDIPs.

Large area III–V infrared focal planes

Jet Propulsion Laboratory is actively developing the III–V based infrared detector and focal plane arrays (FPAs) for remote sensing and imaging applications. Currently, we are working on Superlattice detectors, multi-band quantum well infrared photodetectors (QWIPs), and quantum dot infrared photodetector (QDIPs) technologies suitable for high pixel-pixel uniformity and high pixel operability large area imaging arrays. In this paper, we will discuss the demonstration of long-wavelength 1 K × 1 K QDIP FPA, 1 K × 1K QWIP FPA, the first demonstration of the megapixel-simultaneously-readable and pixel-co-registered dual-band QWIP FPA, and demonstration of the first mid-wave and long-wave 1K × 1K superlattice FPA. In addition, we will discuss the advantages of III–V material system in the context of large format infrared FPAs.

Wavelength-tunable InGaAs-capped quantum-dot infrared photodetectors for multi-color detection

A two-terminal quantum-dot infrared photodetector (QDIP) with stacked 5-period InAs/GaAs and InGaAs-capped InAs/GaAs QD structures is investigated in this paper. The device has exhibited distinct responses at mid-wavelength and long-wavelength infrared regions under positive and negative biases, respectively. Also observed for the device are the equal normal absorption ratios under different voltage biases for the device under either MWIR or LWIR ranges. The device has revealed its potential in the application of voltage-tunable and multi-color detections.

Light direction-dependent plasmonic enhancement in quantum dot infrared photodetectors

Plasmonic enhancement of a quantum dot infrared photodetector (QDIP) integrated with a metal photonic crystal (MPC) depends on the direction of the incident light, air-side versus substrate-side illumination. Compared with air-side illumination, substrate-side illumination on the same photodetector results in more than 2× enhancement in detectivity. This is explained by more efficient excitation of surface plasma waves (SPWs) at the MPC/QDIP interface in the back-side geometry. The air/MPC/semiconductor structure is optically asymmetric and has different SPW coupling leading to higher photoresponse for substrate-side illumination. This agrees with simulation and provides direct evidence that the detectivity enhancement is due to the coupling to SPWs and is crucially affected by light incident direction.