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Growth and study of quantum dots infrared photodetectors coupled with parabolic quantum wells

Growth and study of quantum dots infrared photodetectors coupled with parabolic quantum wells. Germano Maioli Penello. IR photodetectors. Astronomy; Gas detection; Military; Agriculture; Wireless comunication. Prediction of failures. Industry plants. Security. Health.

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Growth and study of quantum dots infrared photodetectors coupled with parabolic quantum wells

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  1. Growth and study of quantum dots infrared photodetectors coupled with parabolic quantum wells Germano Maioli Penello

  2. IR photodetectors • Astronomy; • Gas detection; • Military; • Agriculture; • Wireless comunication. Prediction of failures Industry plants Security Health http://www.nationalinfrared.com/

  3. Quantum dots photodetectors[1] • Normal incidence allowed; • Lower dark current; • Difficulty in the control of dots size; • Difficulty in the control of dots density.

  4. Quantum dots photodetectors[1,2] • Normal incidence allowed; • Lower dark current; • Difficulty in the control of dots size; • Difficulty in the control of dots density. Alternative: Coupling a quantum well to the quantum dot makes easier to control the desired energy levels for the selected transitions.

  5. III-V semiconductors As we use InP substrate in these samples, a good energy gap control can be done managing In, Ga, Al, and As. The energy gap can be changed from InAlAs to InGaAs, ~1,5 eV to ~0.8 eV , respectively.

  6. III-V semiconductors[3] Egap(z) = 0,76 + 0,49 z + 0,20 z2 (eV )

  7. Parabolic quantum well (PQW) InGaAl0,20As Egap(z)=0,76 + 0,49 z + 0,20 z2(eV ) (In0.53Ga0.47As)1-z(In0.52Al0.48As)z InGaAs Thickness (a.u.) Our mass flow controller (MFC) is not subtle enough to the range desired in the midle of the parabola (near 0% of Al).

  8. Quaternary InP Conduction Band Conduction Band Growth direction Growth direction Quantum dot inside the PQW w w Real growth Ideal growth

  9. In order to study the influence of the parabola thickness, we grew four samples with different parabolas width. Final structure 5 nm 3 nm Sample # w (nm) 8 nm 1164 5.5 1165 8.4 1166 11.0 1167 16.8 99 nm w 16 nm w x10

  10. Computational results (1D simulations) 1164 w = 5.5 nm 1165 w = 8.4 nm 1166 w = 11.0 nm 1167 w = 16.8 nm

  11. Experimental results (intraband - FTIR) 1164 1165 1166 1167

  12. Photocurrent Results x Simulation As the thickness of the well is higher, the transition energy is lower (except for 1167) Good agreement between the experimental and the computational results. Calculation based on a 1D approximation!

  13. Interesting results – Current reversal Wavelength (µm) Indicatives of current reversal comproved by a direct current measurement. Normalized photocurrent Energy (eV)

  14. Current reversal behavior An indicative of current reversal is observed looking that different peaks have null intensity at different bias.

  15. First 3D calculation Sample 1164

  16. Agradecimentos • Mauricio P. Pires, Patrícia L. de Souza • Rudy M. S. Kawabata, Daniel N. Micha • Deborah Alvarenga, Paulo S. S. Guimarães, Carlos Parra • Gustavo S. Vieira

  17. References [1] A. Rogalski. Infrared detectors: status and trends. Progress in quantum Electronics, 27(2-3):59-210, 2003. [2] S. Krishna. Quantumdots-in-a-well infrared photodetectors. Infrared Physics and Technology, 47(1-2):153-163, 2005. [3] I. Vurgaftman, J. R. Meyer, and L. R. Ram-Mohan. Band parameters for III-V compound semiconductors and their alloys. Journal of applied physics, 89:5815, 2001.

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