1 / 16

Impact of Non-Linear Piezoelectricity on Excitonic Properties of

Impact of Non-Linear Piezoelectricity on Excitonic Properties of III-N Semiconductor Quantum Dots. Joydeep Pal Microelectronics and Nanostructures Group School of Electrical and Electronic Engineering. Outline. Contents. Introduction to Piezoelectric Effect

barney
Download Presentation

Impact of Non-Linear Piezoelectricity on Excitonic Properties of

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Impact of Non-Linear Piezoelectricity on Excitonic Properties of III-N Semiconductor Quantum Dots Joydeep Pal Microelectronics and Nanostructures Group School of Electrical and Electronic Engineering

  2. Outline Contents • Introduction to Piezoelectric Effect • Physical Parameters: Bulk and Strained III-N systems • Piezoelectric field in Quantum Wells: Impact of the Non-linear piezoelectric effect • Excitonic properties of Quantum Dots: Study on InGaN QDs

  3. + + + - + - + + + + Piezoelectric Polarisation Piezoelectricity in III-V semiconductors Applied Strain 4 identical sp3 orbitals Only 3 identical sp3 orbitals

  4. In-plane Strain δr Shear Strain Atomic Displacement model W. A. Harrison: Electronic Structure and Properties of Solids, Dover, New York (1989). Material parameters : αp: bond polarity ZH*: effective ionic charge (depends on αp) M. Migliorato et al, Phys. Rev. B 74, 245332 (2006), R.Garg et al,Appl. Phys. Lett. 95, 041912 (2009) J. Pal et al, Phys. Rev. B 84, 085211 (2011)

  5. Physical parameters of Group-III-Nitrides Parameters GaN AlN InN a (Ǻ) 3.155 3.063 3.523 c (Ǻ) 5.149 4.906 5.725 u (Ǻ) 0.376 0.382 0.377 Z* 2.583 2.553 2.850 αp 0.517 0.511 0.578 Z*H 0.70 0.85 0.65 e31(C/m2) -0.55 (-0.55exp) -0.6 (-0.6exp) -0.55 (-0.55exp) e33 (C/m2) 1.05 (1.12exp) 1.47 (1.50exp) 1.07 (0.95exp) e15 (C/m2) -0.57(-0.38th) -0.6 (-0.48exp) -0.65 (-0.44th) e311(C/m2) 6.185 5.850 5.151 e333(C/m2) -8.090 -10.750 -6.680 e133(C/m2) 1.543 4.533 1.280 Psp (C/m2) -0.007 (-0.029th) -0.051 (-0.081th) -0.012 (-0.032th) Total Polarization with Second Order effects J. Pal et al, Phys. Rev. B 84, 085211 (2011)

  6. Total Polarization (PT) v Strain J. Pal et al, Phys. Rev. B 84, 085211 (2011)

  7. Spontaneous Polarization (Psp) in Alloys J. Pal et al, Phys. Rev. B 84, 085211 (2011)

  8. Piezoelectric field in Binary III-N Quantum Wells Quantum Well Experiment This work Previous work Lw/Lb (MV/cm) (MV/cm) (MV/cm)  GaN/AlN 10.20 10.30 10.65 2.6/100  GaN/AlN 8.00 8.06 8.43 2.5/6 GaN/AlN 10.00 ±1.00 9.00 ±0.50 6.0 ±1.00 (0.8 ±0.26)/ (2.8±0.52) GaN/AlN 5.04 5.06 4.76 2.3/1.9 GaN/AlN 6.07 6.072 6.55 1.4/1.9 InN/GaN 9.25th(8.13 th) 9.13(5.9) 6.71 4/6  InN/GaN 5.21th(11.17th) 5.71(9.23) 4.11 6/4   InN/GaN 5.89th(8.61th) 6.4(8.57) 5.11 8/6 J. Pal et al, Phys. Rev. B 84, 085211 (2011)

  9. Piezoelectric field in Binary III-N Quantum Wells J. Pal et al, Opt Quant Electron (2011) (published online)

  10. Piezoelectric field in Ternary III-N Quantum Wells Quantum Well Experiment This work Previous work Lw/Lb (kV/cm) (kV/cm) (kV/cm) Al0.17Ga0.83N/GaN 760 760 1205 3/5 Al0.65Ga0.35N/GaN 2000 2090 2170 6/3 GaN/In0.06Ga0.94N 605 610 544 3/3 GaN/In0.09Ga0.91N 1000 960 766 3/3 GaN/In0.11Ga0.89N 1330 1310 1210 3/3 GaN/In0.12Ga0.88N 1600 1603 1500 3/6 GaN/In0.22Ga0.78N 3090 3097 3132 3/8 J. Pal et al, Phys. Rev. B 84, 085211 (2011)

  11. Excitonic Structure in III-N Alloy Quantum Dots Exciton X0 Biexciton 2X Biexcitonic Shift : Bxx = Exx - 2Ex Optimization Function: Ξ = Bxx*ln(px(x)/px(0)) • Exx and Ex calculated with full configuration interaction (CI) Hamiltonian (Ne=12, Nh=18) • parallel kppw 8 Band k.p calculation including • Strain • Spin-Orbit interaction • 2nd Order Piezoelectricity • Spontaneous Polarization • Shape (Aspect Ratio D/h) Exx: Biexciton Energy Ex: Exciton Energy A. Mohan et al, Nphoton.2010.2 (2010) S. Tomic, A. Sunderland, I. Bush, J. Mat. Chem. 16, 1963 (2006) S. Tomić & N. Vukmirović, Physical Review B 79, 245330 (2009)

  12. Excitonic Structure in III-N Alloy Quantum Dots Biexciton shift: Alloy composition dependence in InGaN Quantum dots Application : Generation of Entangled Photon Source, Multi Exciton Generation (MEG) Solar Cells

  13. Excitonic Structure in III-N Alloy Quantum Dots Exx = 2Ex D/h = 5 Bound Biexciton: Light emission at different energies by tuning the alloy content in the InGaN Quantum dots Main Application : Entangled photon source covering the visible light spectra

  14. Excitonic Structure in III-N Alloy Quantum Dots Optimization function for Single Photon Source : Tunability in the InGaN Quantum dots (based on the In content) Application : Generation of Single Photon Source

  15. Excitonic Structure in III-N Alloy Quantum Dots Maximum values of Optimization Function (Ξ) Optimization function : Best suitable light emission energy range dependent on alloy composition in InGaN Quantum dots Main Application : Widely tunable single photon source

  16. Conclusions & Acknowledgements • A new improved set of piezoelectric coefficients for III-N has been presented. Second order effects are sizeable. • Most notably the spontaneous polarization is substantially smaller than previously believed. • Predictions of the binding energy of excitons in InGaN QDs show that it is possible to obtain entangled photons for a large range of compositions • Since photons appear to be possible across the visible range our study suggests that nitride based QDs should be further investigated experimentally as single photon sources • Many thanks and gratitude go to: • Max Migliorato, Geoffrey Tse, Vesel Haxha, Raman Garg (University of Manchester) • Stanko Tomić (University of Salford) • Robert Young (University of Lancaster) • CASTEP Development Group, Matt Probert & Phil Hasnip (York) • High Performance Computing (HPC) facility in Manchester (University of Manchester) and SCARF in STFC Rutherford Appleton Lab

More Related