Experimental and atomistic theoretical study of degree of polarization from multilayer InAs/GaAs quantum dot stacks

Muhammad Usman, Tomoya Inoue, Yukihiro Harda, Gerhard Klimeck, and Takashi Kita
Phys. Rev. B 84, 115321 – Published 23 September 2011

Abstract

Recent experimental measurements, without any theoretical guidance, showed that isotropic polarization response can be achieved by increasing the number of quantum-dot (QD) layers in a QD stack. Here we analyze the polarization response of multilayer QD stacks containing up to nine QD layers by linearly polarized photoluminescence (PL) measurements and by carrying out a systematic set of multimillion atom simulations. The atomistic modeling and simulations allow us to include correct symmetry properties in the calculations of the optical spectra, a factor critical to explain the experimental evidence. The values of the degree of polarization (DOP) calculated from our model follows the trends of the experimental data. We also present detailed physical insight by examining strain profiles, band edges diagrams, and wave function plots. Multidirectional PL measurements and calculations of the DOP reveal a unique property of InAs QD stacks that the TE response is anisotropic in the plane of the stacks. Therefore, a single value of the DOP is not sufficient to fully characterize the polarization response. We explain this anisotropy of the TE modes by orientation of hole-wave functions along the [1¯10] direction. Our results provide a new insight that isotropic polarization response measured in the experimental PL spectra is due to two factors: (i) TM001-mode contributions increase due to enhanced intermixing of HH and LH bands, and (ii) TE110-mode contributions reduce significantly due to hole-wave function alignment along the [1¯10] direction. We also present optical spectra for various geometry configurations of QD stacks to provide a guide to experimentalists for the design of multilayer QD stacks for optical devices. Our results predict that the QD stacks with identical layers will exhibit lower values of the DOP than the stacks with nonidentical layers.

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  • Received 27 May 2011

DOI:https://doi.org/10.1103/PhysRevB.84.115321

©2011 American Physical Society

Authors & Affiliations

Muhammad Usman1,*, Tomoya Inoue2, Yukihiro Harda2, Gerhard Klimeck3, and Takashi Kita2

  • 1Tyndall National Institute, Lee Maltings, Dyke Parade, Cork, Ireland
  • 2Department of Electrical and Electronic Engineering, Graduate School of Engineering, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
  • 3Purdue University, Network for Computational Nanotechnology, Birck Nanotechnology Center, 1205 West State Street, West Lafayette, Indiana 47907, USA

  • *usman@alumni.purdue.edu

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Issue

Vol. 84, Iss. 11 — 15 September 2011

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