InAs Quantum Dots in AlAs/GaAs Short Period Superlattices: Structure, Optical Characteristics and Laser Diodes

2001 ◽  
Vol 707 ◽  
Author(s):  
Vadim Tokranov ◽  
M. Yakimov ◽  
A. Katsnelson ◽  
K. Dovidenko ◽  
R. Todt ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Room Temperature ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Inas Quantum Dots ◽  
Transmission Electron ◽  
Short Period ◽  
Short Period Superlattices ◽  
Emitting Lasers ◽  
Cladding Layers

ABSTRACTThe influence of two monolayer - thick AlAs under- and overlayers on the formation and properties of self-assembled InAs quantum dots (QDs) has been studied using transmission electron microscopy (TEM) and photoluminescence (PL). Single sheets of InAs QDs were grown inside a 2ML/8ML AlAs/GaAs short-period superlattice with various combinations of under- and overlayers. It was found that 2.4ML InAs QDs with GaAs underlayer and 2ML AlAs overlayer exhibited the lowest QD surface density of 4.2x1010 cm-2 and the largest QD lateral size of about 19 nm as compared to the other combinations of cladding layers. This InAs QD ensemble has also shown the highest room temperature PL intensity with a peak at 1210 nm and the narrowest linewidth, 34 meV. Fabricated edge-emitting lasers using triple layers of InAs QDs with AlAs overlayer demonstrated 120 A/cm2 threshold current density and 1230 nm emission wavelength at room temperature. Excited state QD lasers have shown high thermal stability of threshold current up to 130°C.

InAs quantum dots in AlAs/GaAs short period superlattices: structure, optical characteristics and laser diodes

2001 ◽  
Vol 692 ◽  
Author(s):  
Vadim Tokranov ◽  
M. Yakimov ◽  
A. Katsnelson ◽  
K. Dovidenko ◽  
R. Todt ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Room Temperature ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Inas Quantum Dots ◽  
Transmission Electron ◽  
Short Period ◽  
Short Period Superlattices ◽  
Emitting Lasers ◽  
Cladding Layers

AbstractThe influence of two monolayer - thick AlAs under- and overlayers on the formation and properties of self-assembled InAs quantum dots (QDs) has been studied using transmission electron microscopy (TEM) and photoluminescence (PL). Single sheets of InAs QDs were grown inside a 2ML/8ML AlAs/GaAs short-period superlattice with various combinations of under- and overlayers. It was found that 2.4ML InAs QDs with GaAs underlayer and 2ML AlAs overlayer exhibited the lowest QD surface density of 4.2×1010 cm-2 and the largest QD lateral size of about 19 nm as compared to the other combinations of cladding layers. This InAs QD ensemble has also shown the highest room temperature PL intensity with a peak at 1210 nm and the narrowest linewidth, 34 meV. Fabricated edge-emitting lasers using triple layers of InAs QDs with AlAs overlayer demonstrated 120 A/cm2 threshold current density and 1230 nm emission wavelength at room temperature. Excited state QD lasers have shown high thermal stability of threshold current up to 130°C.

Shape Engineered InAs Quantum Dots with Stabilized Electronic Properties

2002 ◽  
Vol 737 ◽  
Author(s):  
V. Tokranov ◽  
M. Yakimov ◽  
A. Katsnelson ◽  
K. Dovidenko ◽  
M. Lamberti ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Room Temperature ◽  
State Energy ◽  
Growth Parameters ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Temperature Threshold ◽  
Inas Quantum Dots ◽  
Subsequent Heating ◽  
Heating Up

ABSTRACTWe have studied the influence of overgrowth procedure and a few monolayer-thick AlAs overlayer on the properties of self-assembled InAs quantum dots (QDs) using scanning electron microscopy (SEM) and photoluminescence (PL). PL spectroscopy was used to optimize optical properties of the QDs by shape engineering (QD truncation) through adjustment of the thickness of overlayers and temperature of the subsequent heating. QDs with 6 nm - thick overlayer with subsequent heating up to 560°C was found to have the highest PL intensity at room temperature and the lowest FWHM, 29 meV. Ground state energy of the truncated QDs is very stable against variations of growth parameters. 1.23 μm edge-emitting laser of triple-layer QD structure demonstrated room temperature threshold current density, 74 A/cm2.

MBE Growth and Characterization of Composite InAlAs/In(Ga)As Vertically Aligned Quantum Dots

1999 ◽  
Vol 571 ◽  
Author(s):  
A. R. Kovsh ◽  
A. E. Zhukov ◽  
A.Yu. Egorov ◽  
N. N. Maleev ◽  
S. S. Mikhrin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Continuous Wave ◽  
Areal Density ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Spontaneous Transformation ◽  
Continuous Wave Output Power ◽  
Transmission Electron ◽  
Internal Loss ◽  
Photoluminescence Studies

ABSTRACTIn the present work we study the effect of vertical alignment in the quantum dot array formed by successive deposition of several rows of InAlAs and InGaAs quantum dots separated by thin AIGaAs spacer layers. Transmission electron microscopy and photoluminescence studies revealed that the InAlAs QDs characterized by high areal density force InGaAs to be transformed into the denser array as compared to the case of spontaneous transformation. Using denser array of composite quantum dots in the active region of a diode laser leads to the increase in modal gain, decrease in internal loss, and decrease in the threshold current density for short cavity diodes. Room temperature continuous wave output power as high as 3.3 W at 0.87 µm is achieved.

Formation of Stacked Self-Assembled InAs Quantum Dots in GaAs Matrix for Laser Applications

1995 ◽  
Vol 417 ◽  
Author(s):  
V. M. Ustinov ◽  
A. Yu. Egorov ◽  
A. E Zhukov ◽  
N. N. Ledentsov ◽  
M. V. Maksimov ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Current Density ◽  
Ground State ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Laser Applications ◽  
Inas Quantum Dots ◽  
Gaas Matrix ◽  
Single Sheet ◽  
Thermal Stability Of

AbstractVertically coupled InAs quantum dots have been synthesized by MBE through successive deposition of InAs dot sheets and thin GaAs spacers. The energy of ground state transition in PL spectra has been found to depend on a number of dot sheets and the spacer width. Injection laser based on vertically coupled quantum dots demonstrated lasing via the ground state of quantum dots in the entire 80K-300K temperature range. Lower threshold current density and wider range of the thermal stability of threshold current density as compared to the single sheet quantum dot laser have been observed.

3D Arrays of Quantum Dots for Laser Applications

1996 ◽  
Vol 421 ◽  
Author(s):  
N.N. Ledentsov ◽  
J. Böhrer ◽  
D. Bimberg ◽  
S.V. Zaitsev ◽  
V.M. Ustinov ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Laser Applications ◽  
Nanoscale Structures ◽  
Self Organized ◽  
Gaas Matrix ◽  
Short Period ◽  
Ordered Array ◽  
Differential Efficiency

AbstractWe have fabricated and studied injection lasers based on vertically coupled quantum dots (VECODs). VECODs are self-organized during alternate short-period GaAs-InAs (InGaAs) depositions after InAs (or InGaAs) pyramids are formed on a GaAs (100). The resulting arrangement represents laterally ordered array of nanoscale structures inserted in a GaAs matrix, where each structure is composed of several vertically merging InAs (or InGaAs) parts. VECODs are introduced in the active region of GaAs-AlGaAs double heterostructure laser. The threshold current density remarkably decreases with increase in number of periods (N) of the VECOD (down to 90 A cm-2 at 300K for N=10). The differential efficiency increases with N and the lasing occurs through ground state of quantum dot exciton up to room temperature (λ=1.05 μm).

scholarly journals Влияние конструкции эпитаксиальной структуры и параметров роста на характеристики метаморфных лазеров оптического диапазона 1.46 мкм на основе квантовых точек на положках GaAs

2018 ◽  
Vol 52 (10) ◽  
pp. 1191
Author(s):  
М.В. Максимов ◽  
А.М. Надточий ◽  
Ю.М. Шерняков ◽  
А.С. Паюсов ◽  
А.П. Васильев ◽  
...  
Keyword(s):  
Active Region ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Threading Dislocations ◽  
Optical Range ◽  
Broad Area ◽  
Gaas Substrates ◽  
Pulsed Mode ◽  
Short Period ◽  
Short Period Superlattices

AbstractThe characteristics of lasers of the 1.44–1.46-μm optical range grown on GaAs substrates using a metamorphic buffer are studied. The active region of the laser contains 10 rows of InAs/In_0.4Ga_0.6As/In_0.2Ga_0.8As quantum dots. It is shown that the use of special selective high-temperature annealing along with the application of short-period In_0.2Ga_0.8As/In_0.2Al_0.3Ga_0.5As short-period superlattices makes it possible to substantially decrease the density of threading dislocations in the active region. A threshold current density of 1300 A cm^–2, external differential quantum efficiency of 38%, and maximal pulsed-mode output power of 13 W are attained for a laser with a broad area 3 mm in length.

scholarly journals In Situ Observation of Electron-Beam-Induced Formation of Nano-Structures in PbTe

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 163
Author(s):  
Iryna Zelenina ◽  
Igor Veremchuk ◽  
Yuri Grin ◽  
Paul Simon
Keyword(s):  
Electron Beam ◽  
Gas Phase ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Atomic Scale ◽  
In Situ Observation ◽  
Nano Structures ◽  
Transmission Electron ◽  
Initial Crystal

Nano-scaled thermoelectric materials attract significant interest due to their improved physical properties as compared to bulk materials. Well-shaped nanoparticles such as nano-bars and nano-cubes were observed in the known thermoelectric material PbTe. Their extended two-dimensional nano-layer arrangements form directly in situ through electron-beam treatment in the transmission electron microscope. The experiments show the atomistic depletion mechanism of the initial crystal and the recrystallization of PbTe nanoparticles out of the microparticles due to the local atomic-scale transport via the gas phase beyond a threshold current density of the beam.

L-cysteine functionalized graphene quantum dots for sub-ppb detection of As (III)

2021 ◽  
Author(s):  
Md. Farhan Naseh ◽  
Neelam Singh ◽  
Jamilur R. Ansari ◽  
Ashavani Kumar ◽  
Tapan Sarkar ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Quantum Dots ◽  
Room Temperature ◽  
Graphene Quantum Dots ◽  
Optical Characterization ◽  
Functionalized Graphene ◽  
Transmission Electron ◽  
Sensitivity And Selectivity ◽  
Structural Characterizations

Abstract Here, we report functionalized graphene quantum dots (GQDs) for the optical detection of arsenic at room temperature. GQDs with the fluorescence of three fundamental colors (red, green, and blue) were synthesized and functionally capped with L-cysteine (L-cys) to impart selectively towards As (III) by exploiting the affinity of L-cys towards arsenite. The optical characterization of GQDs was carried out using UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy, and fluorescence spectrometry and the structural characterizations were performed using transmission electron microscopy. The fluorescence results showed instantaneous quenching in intensity when the GQDs came in contact with As (III) for all test concentrations over a range from 0.025 ppb to 25 ppb, which covers the permissible limit of arsenic in drinking water. The experimental results suggested excellent sensitivity and selectivity towards As (III).

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