12 research outputs found
Self-assembled strained nanostructures for light emission grown using molecular beam epitaxy
No full textIII-V nanostructures are widely researched for applications in dislocation-resistant light emitters for photonic integrated circuits, quantum computing and single photon emitters. The 0D nanostructures include quantum dots (QDs), dot in a well (DWELLs), sub-monolayer QDs and droplet epitaxy QDs, while 1D elongated structures include quantum dashes and nanowires (NWs). The optical properties of nanostructures can be controlled through size, composition, strain and band-offsets during epitaxial growth and can be tailored precisely to emit light with photon energies suited to the application, spanning 0.2-2.0 eV. This thesis explores two novel QD based light emitters in the visible and near-infrared wavelength regime. In the first part of the thesis, we demonstrate the growth and characterization of tensile strained Ge QDs and Ge NWs phase segregated in the III-V matrix via Volmer-Weber growth mode emitting at 1200 nm. The second part of the thesis demonstrates the dislocation tolerance of compressively strained InP QDs grown on lattice-matched GaAs and lattice-mismatched Si substrate via Stranski-Krastanov growth mode emitting at 713 nm.
The first part of the thesis explores the growth of tensile strained Ge QDs and NWs phase segregated in the III-V matrix. Epitaxial growth of phase segregated Ge nanostructures embedded within III-V compound semiconductors is a promising way to achieve a high biaxial tensile strain along with precise control of nanostructure density, size and morphology. Here we demonstrate growth of phase-segregated Ge quantum dots (QDs) and compare them to our previously reported Ge nanowires (NWs); both are strained to an In0.52Al0.48As matrix with a high biaxial tensile strain of 3.6%. Despite the similar growth conditions, there exist pronounced differences in the lateral size and planar density of Ge QDs and Ge NWs, with Ge QDs showing significantly larger size, lower density and structural anisotropy along the in-plane [1-10] direction. In addition to the difference in morphology, Ge QDs are shown to be more prone to plastic relaxation by formation of dislocations and stacking faults, which we attribute to their larger in-plane size. Finally, tensile Ge QDs are shown to exhibit strong room-temperature photoluminescence at 1176 nm, which is blueshifted from the case of Ge NWs.
In the second part of the thesis, we demonstrate epitaxial InP QDs on GaAs on Si virtual substrates with room-temperature photoluminescence (PL) intensity nearly identical to those grown on GaAs substrates. The similarity in PL characteristics is remarkable considering that the active region on the GaAs/Si virtual substrate has a threading dislocation density (TDD) of ~3×10^7 cm-2, as compared to the bulk GaAs substrate with TDD 50× improvement in the luminescence intensity of InP QDs annealed at ~700⁰C for 100 minutes without observable structural degradation or blue-shift in the PL spectrum.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-05-01The student, Pankul Dhingra, accepted the attached license on 2019-04-25 at 12:06.The student, Pankul Dhingra, submitted this Thesis for approval on 2019-04-25 at 12:16.This Thesis was approved for publication on 2019-04-25 at 14:10.DSpace SAF Submission Ingestion Package generated from Vireo submission #13914 on 2019-08-22 at 16:23:56Made available in DSpace on 2019-08-23T20:48:26Z (GMT). No. of bitstreams: 2
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Previous issue date: 2019-04-25Embargo set by: Seth Robbins for item 112387
Lift date: 2021-08-23T20:48:32Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 112387 on 2021-08-24T09:15:38Z
Design, defect reduction, and dislocation tolerance of red lasers on Si (001)
No full textSubmission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2024-05-01The student, Pankul Dhingra, accepted the attached license on 2022-04-21 at 16:34.The student, Pankul Dhingra, submitted this Dissertation for approval on 2022-04-21 at 16:45.This Dissertation was approved for publication on 2022-04-22 at 12:44.DSpace SAF Submission Ingestion Package generated from Vireo submission #17894 on 2022-11-11 at 12:58:04Monolithic integration of III-V optoelectronic devices with silicon nitride photonics technology could open a wide range of on-chip applications spanning a wide wavelength range of 400 – 4000 nm. The wavelength palette of III-V lasers on Si spans 400 nm – 11 μm with the development of nitride, arsenide and antimonide quantum well (QW) and quantum dot (QD) lasers, leaving a crucial gap in the development of red lasers on Si with 630 – 750 nm emission using phosphide active region. In this dissertation, we demonstrate the development of InGaP QW and InP QD lasers on GaAs and Si (001) substrates, integrated on silicon nitride photonic integrated circuits using molecular beam epitaxy. It is found that InP QDs on Si (001) show a photoluminescence intensity similar to counterparts grown on GaAs (001), despite a threading dislocation density (TDD) of 3.3×107 cm-2. In contrast, InGaP QWs on Si (001), with the same TDD, show 9× degradation in PL intensity compared to QWs on GaAs. We demonstrate post-growth annealing as an essential step towards demonstration of MBE-grown phosphide lasers, with InGaP single quantum well (SQW) and InP multiple quantum dot (MQD) lasers on GaAs operating with a threshold current density (Jth) of 170 A/cm2 and 230 A/cm2 on GaAs (001), the lowest continuous wave (CW) Jth by any growth technique. We also demonstrate strategies to reduce the TDD of epitaxial GaAs/Si from > 4×108 cm-2 to 6×106 cm-2 by using dislocation filtering techniques. Utilizing low-TDD GaAs/Si templates and low-Jth active region design, we show the first CW- room temperature (RT) InGaP SQW and InP MQD lasers on GaAs/Si (001) with Jth of 550 A/cm2 and 690 A/cm2, respectively, the lowest reported to the best of our knowledge. The higher dislocation tolerance of phosphide lasers, compared to arsenide lasers, can be attributed to the low carrier diffusivity in phosphides. The dissertation also presents preliminary results on the integration of visible optoelectronic devices on photonic integrated circuits utilizing silicon nitride waveguides on Si substrates
Structure of light
No full textIs it not fascinating when engineering materials on an atomic scale yields macroscopic observables imageable through a smartphone? University of Illinois at Urbana-Champaign has a historical legacy in semiconductor lasers and light-emitting diodes used today in fiber-optic communications, medicine, surgery, optical storage and recently detecting gravitational waves (LIGO). A laser is an intricate device requiring quantum mechanical calculations, precise material growth optimized to the scale of atomic layers, and meticulous device fabrication, all working together in harmony. The image shows my first working semiconductor laser that I designed, grew, and fabricated at Holonyak Micro and Nanotechnology Laboratory. The picture follows >200 failed attempts finally leading to nearly a world record device. While the light inside the laser is generated as visible photons, the far-field structure of light we observe on a wall is a wave interference pattern, a reminder of the wave-particle duality of light. The laser shown comprises a thin 7 nm semiconductor layer capable of generating light power >100 mW, enough to burn a matchstick if focused to a spot! I plan to integrate visible lasers on silicon substrates for low-cost silicon photonics platforms paving the way for applications like integrated optogenetics, biophotonic sensing, and quantum optics.Made available in DSpace on 2021-04-12T22:32:12Z (GMT). No. of bitstreams: 2
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Previous issue date: 202
Self-assembled strained nanostructures for light emission grown using molecular beam epitaxy
No full textIII-V nanostructures are widely researched for applications in dislocation-resistant light emitters for photonic integrated circuits, quantum computing and single photon emitters. The 0D nanostructures include quantum dots (QDs), dot in a well (DWELLs), sub-monolayer QDs and droplet epitaxy QDs, while 1D elongated structures include quantum dashes and nanowires (NWs). The optical properties of nanostructures can be controlled through size, composition, strain and band-offsets during epitaxial growth and can be tailored precisely to emit light with photon energies suited to the application, spanning 0.2-2.0 eV. This thesis explores two novel QD based light emitters in the visible and near-infrared wavelength regime. In the first part of the thesis, we demonstrate the growth and characterization of tensile strained Ge QDs and Ge NWs phase segregated in the III-V matrix via Volmer-Weber growth mode emitting at 1200 nm. The second part of the thesis demonstrates the dislocation tolerance of compressively strained InP QDs grown on lattice-matched GaAs and lattice-mismatched Si substrate via Stranski-Krastanov growth mode emitting at 713 nm.
The first part of the thesis explores the growth of tensile strained Ge QDs and NWs phase segregated in the III-V matrix. Epitaxial growth of phase segregated Ge nanostructures embedded within III-V compound semiconductors is a promising way to achieve a high biaxial tensile strain along with precise control of nanostructure density, size and morphology. Here we demonstrate growth of phase-segregated Ge quantum dots (QDs) and compare them to our previously reported Ge nanowires (NWs); both are strained to an In0.52Al0.48As matrix with a high biaxial tensile strain of 3.6%. Despite the similar growth conditions, there exist pronounced differences in the lateral size and planar density of Ge QDs and Ge NWs, with Ge QDs showing significantly larger size, lower density and structural anisotropy along the in-plane [1-10] direction. In addition to the difference in morphology, Ge QDs are shown to be more prone to plastic relaxation by formation of dislocations and stacking faults, which we attribute to their larger in-plane size. Finally, tensile Ge QDs are shown to exhibit strong room-temperature photoluminescence at 1176 nm, which is blueshifted from the case of Ge NWs.
In the second part of the thesis, we demonstrate epitaxial InP QDs on GaAs on Si virtual substrates with room-temperature photoluminescence (PL) intensity nearly identical to those grown on GaAs substrates. The similarity in PL characteristics is remarkable considering that the active region on the GaAs/Si virtual substrate has a threading dislocation density (TDD) of ~3×10^7 cm-2, as compared to the bulk GaAs substrate with TDD 50× improvement in the luminescence intensity of InP QDs annealed at ~700⁰C for 100 minutes without observable structural degradation or blue-shift in the PL spectrum.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste
Effects of Graded Buffer Design and Active Region Structure on GaAsP Single-Junction Solar Cells Grown on GaP/Si Templates
No full textSupplementary document for Low-threshold InP quantum dot and InGaP quantum well visible lasers on silicon (001) - 5506150.pdf
No full textHigh-temperature L-I, Comparison with literature, I-V characteristics, Cavity length effect
