Photoluminescence of surface InAs quantum dot stacking on multilayer buried quantum dots

2006 ◽  
Vol 89 (24) ◽  
pp. 243124 ◽  
Author(s):  
B. L. Liang ◽  
Zh. M. Wang ◽  
Yu. I. Mazur ◽  
G. J. Salamo
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Inas Quantum Dot

Charge Separation Between Strain Coupled Quantum Dots in a Self-Assembled InAs Quantum Dot Structure

1999 ◽  
Vol 571 ◽  
Author(s):  
W. V. Schoenfeld ◽  
T. Lundstrom ◽  
P. M. Petroff
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Preliminary Data ◽  
Charge Separation ◽  
Electron Hole ◽  
Coupled Quantum Dots ◽  
Time Resolved ◽  
Inas Quantum Dot ◽  
Storage Times ◽  
Time Resolved Photoluminescence

ABSTRACTWe present an InAs QDs structure designed to separate and store photo-generated electron-hole pairs. Charge separation in the structure is demonstrated using power dependent photoluminescence and biased photoluminescence. Preliminary data from time resolved photoluminescence suggest storage times in the device in the μsec range.

MOVPE GROWTH OF THE InP BASED MID-IR EMISSION QUANTUM DOT STRUCTURES

2013 ◽  
Vol 01 (02) ◽  
pp. 1350002
Author(s):  
XIAOHONG TANG ◽  
ZONGYOU YIN ◽  
BAOLIN ZHANG
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Infrared Emission ◽  
Emission Wavelength ◽  
Growth Method ◽  
Metal Organic ◽  
Size Uniformity ◽  
Dot Density ◽  
Inas Quantum Dot ◽  
Ir Emission

In this paper, semiconductor quantum dot structures for mid-infrared emission were self-assembled on InP substrate by using metal–organic vapor phase epitaxy growth. The InAs quantum dots grown at different conditions have been investigated. To improve the grown quantum dot's shape, the dot density and the dot size uniformity, a two-step growth method has been used and investigated. By changing the composition of the In x Ga 1-x As matrix layer of the InAs / In x Ga 1-x As / InP quantum dot structure, emission wavelength of the InAs quantum dot structure has been extended to the longest > 2.35 μm measured at 77 K. For the narrower bandgap semiconductor InAsSb quantum dots, the emission wavelength was measured at > 2.8 μm.

InAs Quantum Dot Development for Enhanced InGaAs Space Solar Cells

2004 ◽  
Vol 851 ◽  
Author(s):  
R. P. Raffaelle ◽  
Samar Sinharoy ◽  
C. William King ◽  
S. G. Bailey
Keyword(s):  
Quantum Dots ◽  
Solar Cells ◽  
Quantum Dot ◽  
Triple Junction ◽  
Spectral Response ◽  
Short Circuit ◽  
Theoretical Estimate ◽  
Inas Quantum Dots ◽  
Bottom Cell ◽  
Inas Quantum Dot

ABSTRACTThe majority of high-efficiency space solar cells being produced today are based on multi-junction devices of lattice-matched III-V materials. An alternative which has been receiving an increasing amount of attention is the lattice mis-matched or metamorphic approach to multi-junction cell development. In the metamorphic triple junction cell under development by ERI and its partners, the InGaAs junction (bottom cell) of the three-cell stack is the current limiting entity, due to the current matching which must be maintained through the device. This limitation may be addressed through the incorporation of InAs quantum dot array into the depletion region of an InGaAs cell. The InAs quantum dots in the InGaAs cell will provide sub-gap absorption and thus improve its short circuit current. This cell could then be integrated into the three-cell stack to achieve a space solar cell whose efficiency exceeds current state-of-the-art standards. A theoretical estimate predicts that a InGaAlP(1.95eV)/InGaAsP(1.35 eV)/InGaAs(1.2 eV) triple junction cell incorporating quantum dots to improve the bottom cell current would have an efficiency exceeding 40%. In addition, theoretical estimates have demonstrated that the use of quantum dot structures may also hold other cell benefits such as improved temperature coefficients and better radiation tolerance, which are especially important for utilization in space. As a first step towards achieving that goal, we have initiated the development of InAs quantum dots on lattice-mismatched InGaAs (1.2 eV bandgap) grown epitaxially on GaAs by metallorganic vapor phase epitaxy (MOVPE). These quantum dots have been characterized via photoluminescence (PL) and atomic force microscopy (AFM). A correlation exists between the quantum dot size and resulting optical band structure and can be controlled via the synthesis parameters. Quantum dots were incorporated into prototype InGaAs devices. A comparison of the resulting photovoltaic efficiency under simulated 1 sun intensity and air mass zero (AM0) illumination and spectral response demonstrated that an improvement in the long-wavelength photoconversion efficiency was achieved through the incorporation of the InAs quantum dots.

Growth and Characterization of InAs Quantum Dot Enhanced Photovoltaic Devices

2007 ◽  
Vol 1017 ◽  
Author(s):  
Seth Martin Hubbard ◽  
Ryne Raffaelle ◽  
Ross Robinson ◽  
Christopher Bailey ◽  
David Wilt ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Spectral Response ◽  
Cell Structure ◽  
Inas Quantum Dots ◽  
Cell Structures ◽  
Dot Density ◽  
Inas Quantum Dot ◽  
Iv Curves

AbstractThe growth of InAs quantum dots (QDs) by organometallic vapor phase epitaxy (OMVPE) for use in GaAs based photovoltaics devices was investigated. Growth of InAs quantum dots was optimized according to their morphology and photoluminescence using growth temperature and V/III ratio. The optimized InAs QDs had sizes near 7×40 nm with a dot density of 5(±0.5)×1010 cm-2. These optimized QDs were incorporated into GaAs based p-i-n solar cell structures. Cells with single and multiple (5x) layers of QDs were embedded in the i-region of the GaAs p-i-n cell structure. An array of 1 cm2 solar cells was fabricated on these wafers, IV curves collected under 1 sun AM0 conditions, and the spectral response measured from 300-1100 nm. The quantum efficiency for each QD cell clearly shows sub-bandgap conversion, indicating a contribution due to the QDs. Unfortunately, the overarching result of the addition of quantum dots to the baseline p-i-n GaAs cells was a decrease in efficiency. However, the addition of thin GaP strain compensating layers between the QD layers, was found to reduce this efficiency degradation and significantly enhance the subgap conversion in comparison to the un-compensated quantum dot cells.

Microanalysis of Self-assembled InAs Quantum Dot Structures Grown for Infrared Detector Applications

2003 ◽  
Vol 794 ◽  
Author(s):  
W.L. Sarney ◽  
J.W. Little ◽  
S. Svensson
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Infrared Detector ◽  
Single Layer ◽  
Far Infrared ◽  
Mbe Growth ◽  
Inas Quantum Dots ◽  
Gaas Matrix ◽  
Inas Quantum Dot ◽  
Vertical Height

ABSTRACTIn an effort to develop materials that are sensitive to mid and far infrared radiation, we examine InAs quantum dot/GaAs matrix multilayer structures grown by molecular beam epitaxy (MBE). Customized electrical and optical properties result from nanoscale-level manipulation of the dots' physical dimensions. The MBE growth temperature can be set to yield dots having the desired lateral dimension; however this leads to dots of insufficient vertical height. It is therefore necessary to grow the dots in a manner that allows independent control of the lateral and vertical dimensions. In this experiment, the vertical dimension is controlled by growing the dots in a multilayer structure with GaAs matrix layers. An initial layer of InAs quantum dots was grown on top of GaAs, followed by a few seconds short growth of GaAs, and then followed by the growth of another layer of InAs dots. The GaAs laterally surrounds, but does not bury, the InAs quantum dots. When the second layer of InAs dots is grown, they tend to self-organize directly on top of the exposed first layer of dots. We then grew a third layer of dots in the same manner. This effectively results in a pseudo-single layer of dots of the desired height which is then completely buried in GaAs. The goal is to develop structures that can be integrated into high operating temperature quantum dot infrared detectors (QDIPs) that have maximum sensitivity, robustness, and portability.

Quantum Dot Solar Cells with Nanoscale Barriers Around Dots: Experiment and Two-Diode Model Analysis

2015 ◽  
Vol 24 (01n02) ◽  
pp. 1520005
Author(s):  
Yanshu Li ◽  
Andrei Sergeev ◽  
Nizami Vagidov ◽  
Vladimir Mitin ◽  
Kimberly Sablon
Keyword(s):  
Quantum Dots ◽  
Solar Cells ◽  
Quantum Dot ◽  
Band Structure ◽  
Photovoltaic Performance ◽  
High Mobility ◽  
Potential Profile ◽  
Selective Doping ◽  
Gaas Devices ◽  
Inas Quantum Dot

Incorporation of quantum dots into the p-n junction of the photovoltaic device provides numerous possibilities for nanoscale control of photoelectron processes via engineering the band structure and nanoscale potential profile. The band structure is determined by the size and shape of quantum dots and width of the wetting layer. The potential profile is formed by selective doping, which leads to the built-in dot charge. To study the effects of the band structure and nanoscale potential barriers on the photovoltaic performance we fabricated and investigated 3-μm base GaAs devices with various InAs quantum dot media and selective doping. All quantum dot devices show significant improvement in conversion efficiency in comparison with the reference cell. The data obtained have been analyzed in frame of the diode model. It was found that the two-diode model with the ideality factors of [Formula: see text] and [Formula: see text] well describes the scope of data. The essential [Formula: see text] component evidences that the Shockley-Read-Hall recombination plays a substantial role in recombination losses. Further optimization of solar cells should be aimed at the formation of potential profile with large barriers that separate quantum dot areas from high mobility conducting channels.

NiAg-graphene quantum dot-graphene hybrid with high oxidase-like catalytic activity for sensitive colorimetric detection of malathion

2021 ◽  
Author(s):  
Xu Dan ◽  
Ruiyi Li ◽  
Qinsheng Wang ◽  
Yongqiang Yang ◽  
Haiyan Zhu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Graphene Oxide ◽  
Catalytic Activity ◽  
Quantum Dot ◽  
Colorimetric Detection ◽  
Graphene Quantum Dots ◽  
Functionalized Graphene ◽  
Graphene Quantum Dot ◽  
Nickel Silver

The paper reports the synthesis of nickel-silver-graphene quantum dot-graphene hybrid. Histidine-functionalized graphene quantum dots (His-GQDs) were bonded to graphene oxide (GO) and then combined with Ni2+ and Ag+ to form...

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