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Full-Text Articles in Physical Sciences and Mathematics
Dreams Of Molecular Beams: Indium Gallium Arsenide Tensile-Strained Quantum Dots And Advances Towards Dynamic Quantum Dots (Moleculare Radiorum Somnia: Indii Gallii Arsenicus Tensa Quanta Puncta Et Ad Dinamicae Quantae Puntae Progressus), Kevin Daniel Vallejo
Boise State University Theses and Dissertations
Through the operation of a molecular beam epitaxy (MBE) machine, I worked on developing the homoepitaxy of high quality InAs with a (111)A crystallographic orientation. By tuning substrate temperature, we obtained a transition from a 2D island growth mode to step- ow growth. Optimized MBE parameters (substrate temperature = 500 °C, growth rate = 0.12 ML/s and V/III ratio ⩾ 40) lead to growth of extremely smooth InAs(111)A films, free from hillocks and other 3D surface imperfections. We see a correlation between InAs surface smoothness and optical quality, as measured by photoluminescence spectroscopy. This work establishes InAs(111)A as a platform …
Single-Photon Generation From Self-Assembled Gaas/Inalas(111)A Quantum Dots With Ultrasmall Fine-Structure Splitting, Christopher F. Schuck, Robert Boutelle, Kevin Silverman, Galan Moody, Paul J. Simmonds
Single-Photon Generation From Self-Assembled Gaas/Inalas(111)A Quantum Dots With Ultrasmall Fine-Structure Splitting, Christopher F. Schuck, Robert Boutelle, Kevin Silverman, Galan Moody, Paul J. Simmonds
Physics Faculty Publications and Presentations
We present a novel semiconductor single-photon source based on tensile-strained (111)-oriented GaAs/InAlAs quantum dots (QDs) exhibiting ultrasmall exciton fine-structure splitting (FSS) of ≤ 8 µeV. Using low-temperature micro-photoluminescence spectroscopy, we identify the biexciton-exciton radiative cascade from individual QDs, which, combined with small FSS, indicates these self-assembled GaAs(111) QDs are excellent candidates for polarization-entangled photon-pair generation.
Strain-Driven Quantum Dot Self-Assembly By Molecular Beam Epitaxy, Kathryn E. Sautter, Kevin D. Vallejo, Paul J. Simmonds
Strain-Driven Quantum Dot Self-Assembly By Molecular Beam Epitaxy, Kathryn E. Sautter, Kevin D. Vallejo, Paul J. Simmonds
Physics Faculty Publications and Presentations
Research into self-assembled semiconductor quantum dots (QDs) has helped advance numerous optoelectronic applications, ranging from solid-state lighting to photodetectors. By carefully controlling molecular beam epitaxy (MBE) growth parameters, we can readily tune QD light absorption and emission properties to access a broad portion of the electromagnetic spectrum. Although this field is now sufficiently mature that QDs are found in consumer electronics, research efforts continue to expand into new areas. By manipulating MBE growth conditions and exploring new combinations of materials, substrate orientations, and the sign of strain, a wealth of opportunities exist for synthesizing novel QD nanostructures with hitherto unavailable …
Quantum Dot Growth On (111) And (110) Surfaces Using Tensile-Strained Self-Assembly, Paul J. Simmonds
Quantum Dot Growth On (111) And (110) Surfaces Using Tensile-Strained Self-Assembly, Paul J. Simmonds
Physics Faculty Publications and Presentations
The self-assembly of epitaxial quantum dots on (001) surfaces, driven by compressive strain, is a widely used tool in semiconductor optoelectronics. In contrast, the growth of quantum dots on (111) and (110) surfaces has historically been a significant challenge. In most cases the strain relaxes rapidly via dislocation nucleation and glide before quantum dots can form. In this paper, we discuss a method for the reliable and controllable self-assembly of quantum dots on both (111) and (110) surfaces, where tensile strain is now the driving force. By showing that tensile-strained self-assembly is applicable to several material systems, we demonstrate the …
Hybrid Type-I Inas/Gaas And Type-Ii Gasb/Gaas Quantum Dot Structure With Enhanced Photoluminescence, Hai-Ming Ji, Baolai Liang, Paul J. Simmonds, Bor-Chau Juang, Tao Yang, Robert J. Young, Diana L. Huffaker
Hybrid Type-I Inas/Gaas And Type-Ii Gasb/Gaas Quantum Dot Structure With Enhanced Photoluminescence, Hai-Ming Ji, Baolai Liang, Paul J. Simmonds, Bor-Chau Juang, Tao Yang, Robert J. Young, Diana L. Huffaker
Physics Faculty Publications and Presentations
We investigate the photoluminescence (PL) properties of a hybrid type-I InAs/GaAs and type-II GaSb/GaAs quantum dot (QD) structure grown in a GaAs matrix by molecular beam epitaxy. This hybrid QD structure exhibits more intense PL with a broader spectral range, compared with control samples that contain only InAs or GaSb QDs. This enhanced PL performance is attributed to additional electron and hole injection from the type-I InAs QDs into the adjacent type-II GaSb QDs. We confirm this mechanism using time-resolved and power-dependent PL.These hybrid QD structures show potential for high efficiency QD solar cell applications.
Strain-Driven Growth Of Gaas(111) Quantum Dots With Low Fine Structure Splitting, Paul J. Simmonds
Strain-Driven Growth Of Gaas(111) Quantum Dots With Low Fine Structure Splitting, Paul J. Simmonds
Physics Faculty Publications and Presentations
Symmetric quantum dots (QDs) on (111)-oriented surfaces are promising candidates for generating polarization-entangled photons due to their low excitonic fine structure splitting(FSS). However, (111) QDs are difficult to grow. The conventional use of compressive strain to drive QD self-assembly fails to form 3D nanostructures on (111) surfaces. Instead, we demonstrate that (111) QDs self-assemble under tensile strain by growing GaAs QDs on an InP(111)A substrate. Tensile GaAs self-assembly produces a low density of QDs with a symmetric triangular morphology. Coherent, tensile QDs are observed without dislocations, and the QDs luminescence at room temperature. Single QD measurements reveal low FSS with …
Tensile Gaas(111) Quantum Dashes With Tunable Luminescence Below The Bulk Bandgap, Paul J. Simmonds
Tensile Gaas(111) Quantum Dashes With Tunable Luminescence Below The Bulk Bandgap, Paul J. Simmonds
Paul J. Simmonds
Strain-based band engineering in quantum dots and dashes has been predominantly limited to compressively strained systems. However, tensile strain strongly reduces the bandgaps of nanostructures, enabling nanostructures to emit light at lower energies than they could under compressive strain. We demonstrate the self-assembled growth of dislocation-free GaAs quantum dashes on an InP(111)B substrate, using a 3.8% tensile lattice-mismatch. Due to the high tensile strain, the GaAs quantum dashes luminesce at 110–240 meV below the bandgap of bulk GaAs. The emission energy is readily tuned by adjusting the size of the quantum dashes via deposition thickness. Tensile self-assembly creates new opportunities …
Effects Of Gaas(Sb) Cladding Layers On Inas/Alassb Quantum Dots, Paul J. Simmonds
Effects Of Gaas(Sb) Cladding Layers On Inas/Alassb Quantum Dots, Paul J. Simmonds
Paul J. Simmonds
The structural and optical properties of InAs self-assembled quantum dots buried in AlAs0.56Sb0.44 barriers can be controlled using GaAs1−xSbx cladding layers. These cladding layers allow us to manage the amount of Sb immediately underneath and above the InAs quantum dots. The optimal cladding scheme has a GaAs layer beneath the InAs, and a GaAs0.95Sb0.05 layer above. This scheme results in improved dot morphology and significantly increased photoluminescence (PL) intensity. Both power-dependent and time-resolved photoluminescence confirm that the quantum dots have type-II band alignment. Enhanced carrier lifetimes in this quantum dot system …
Structural And Optical Properties Of Inas/Alassb Quantum Dots With Gaas(Sb) Cladding Layers, Paul J. Simmonds, Ramesh Babu Laghumavarapu, Meng Sun, Andrew Lin, Charles J. Reyner, Baolai Liang, Diana L. Huffaker
Structural And Optical Properties Of Inas/Alassb Quantum Dots With Gaas(Sb) Cladding Layers, Paul J. Simmonds, Ramesh Babu Laghumavarapu, Meng Sun, Andrew Lin, Charles J. Reyner, Baolai Liang, Diana L. Huffaker
Paul J. Simmonds
We investigate the effect of GaAs1−xSbxcladding layer composition on the growth and properties of InAsself-assembledquantum dots surrounded by AlAs0.56Sb0.44 barriers. Lowering Sb-content in the GaAs1−xSbx improves the morphology of the InAs quantum dots and reduces cladding layer alloy fluctuations. The result is a dramatic increase in photoluminescence intensity from the InAs quantum dots, with a peak at 0.87 eV. The emission energy exhibits a cube root dependence on excitation power, consistent with the type-II band alignment of the quantum dots. The characteristics of this quantum dot system show promise for …
Self-Assembled In0.5Ga0.5As Quantum Dots On Gap, Yuncheng Song, Paul J. Simmonds, Minjoo Larry Lee
Self-Assembled In0.5Ga0.5As Quantum Dots On Gap, Yuncheng Song, Paul J. Simmonds, Minjoo Larry Lee
Paul J. Simmonds
We demonstrate the growth and luminescence of coherently strained In0.5Ga0.5As self-assembled quantum dots on GaP. Cross-sectional and planar-view transmission electron microscopy confirmed the dislocation-free nature of the In0.5Ga0.5As quantum dots and GaP cap layers. Intense photoluminescence from the quantum dots was measured at 80 K and was visible to the unaided eye in ambient lighting. The photoluminescence results show that emission energy can be controlled by varying the In0.5Ga0.5As deposition thickness. In combination with recent advances in the growth of GaP on Si, the In0.5Ga0.5 …
Tensile Strained Iii-V Self-Assembled Nanostructures On A (110) Surface, Minjoo L. Lee, Paul J. Simmonds
Tensile Strained Iii-V Self-Assembled Nanostructures On A (110) Surface, Minjoo L. Lee, Paul J. Simmonds
Paul J. Simmonds
The vast majority of research on epitaxial quantum dots use compressive strain as the driving force for self-assembly on the (001) surface, with InAs/GaAs(001) and Ge/Si(001) being the best-known examples. In this talk, I will discuss our work on determining the feasibility of growing coherent, tensile-strained III-V nanostructures on a (110) surface. GaP on GaAs(110) was chosen as an initial test system. It is hoped that our efforts on self-assembled, tensile-strained dots on a (110) surface will lead the way to new devices exploiting the fundamental differences between the (110) and (001) surfaces. Furthermore it is anticipated that this work …
Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie
Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie
Paul J. Simmonds
The authors present a quantum dot (QD) based single photon detector operating at a fiber optic telecommunication wavelength. The detector is based on an AlAs/In0.53Ga0.47As/AlAs double-barrier resonant tunneling diode containing a layer of self-assembled InAs QDs grown on an InP substrate. The device shows an internal efficiency of about 6.3% with a dark count rate of 1.58 × 10−6 ns−1 for 1310 nm photons.
Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie
Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie
Paul J. Simmonds
The authors report the results of a detailed study of the effect of growth conditions, for molecular beam epitaxy, on the structural and optical properties of self-assembled InAs quantum dots (QDs) on In0.524Al0.476As. InAs QDs both buried in, and on top of, In0.524Al0.476As were analyzed using photoluminescence (PL) and atomic force microscopy. InAs QD morphology and peak PL emission wavelength both scale linearly with deposition thickness in monolayers (MLs). InAs deposition thickness can be used to tune QD PL wavelength by 170 nm/ML, over a range of almost 700 nm. Increasing growth …