Diffusion process of excitons in the wetting layer and their trapping by quantum dots in sparsely spaced InAs quantum dot systems

2011 ◽  
Vol 98 (13) ◽  
pp. 133109 ◽  
Author(s):  
M. Ohmori ◽  
P. Vitushinskiy ◽  
H. Sakaki
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Diffusion Process ◽  
Wetting Layer ◽  
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.

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

scholarly journals Quantum Confined Stark Effect on the Linear and Nonlinear Optical Properties of SiGe/Si Semi Oblate and Prolate Quantum Dots Grown in Si Wetting Layer

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1513
Author(s):  
Varsha ◽  
Mohamed Kria ◽  
Jawad El Hamdaoui ◽  
Laura M. Pérez ◽  
Vinod Prasad ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Quantum Dot ◽  
Electric Field ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Wetting Layer ◽  
Non Linear ◽  
Linear Optical Properties ◽  
Linear Optical

We have studied the parallel and perpendicular electric field effects on the system of SiGe prolate and oblate quantum dots numerically, taking into account the wetting layer and quantum dot size effects. Using the effective-mass approximation in the two bands model, we computationally calculated the extensive variation of dipole matrix (DM) elements, bandgap and non-linear optical properties, including absorption coefficients, refractive index changes, second harmonic generation and third harmonic generation as a function of the electric field, wetting layer size and the size of the quantum dot. The redshift is observed for the non-linear optical properties with the increasing electric field and an increase in wetting layer thickness. The sensitivity to the electric field toward the shape of the quantum dot is also observed. This study is resourceful for all the researchers as it provides a pragmatic model by considering oblate and prolate shaped quantum dots by explaining the optical and electronic properties precisely, as a consequence of the confined stark shift and wetting layer.

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.

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