Interface Roughness, Carrier Localization, and Wave Function Overlap in c-Plane (In,Ga)N/GaN Quantum Wells: Interplay of Well Width, Alloy Microstructure, Structural Inhomogeneities, and Coulomb Effects

Daniel S. P. Tanner, Joshua M. McMahon, and Stefan Schulz
Phys. Rev. Applied 10, 034027 – Published 14 September 2018

Abstract

In this work, we present a detailed analysis of the interplay of Coulomb effects and different mechanisms that can lead to carrier-localization effects in c-plane (In,Ga)N/GaN quantum wells. As mechanisms for carrier localization, we consider here effects introduced by random alloy fluctuations as well as structural inhomogeneities such as well-width fluctuations. Special attention is paid to the impact of the well width on the results. All calculations have been carried out in the framework of atomistic tight-binding theory. Our theoretical investigations show that independent of the well widths studied here, carrier-localization effects due to built-in fields, well-width fluctuations, and random-alloy fluctuations dominate over Coulomb effects in terms of charge-density redistributions. However, the situation is less clear cut when the well-width fluctuations are absent. For a large well width (approximately >2.5nm), charge-density redistributions are possible, but the electronic and optical properties are basically dominated by the out-of-plane carrier separation originating from the electrostatic built-in field. The situation changes for lower well widths (<2.5nm), where the Coulomb effect can lead to significant charge-density redistributions and, thus, might compensate for a large fraction of the spatial in-plane wave-function separation observed in a single-particle picture. Given that this in-plane separation has been regarded as one of the main drivers behind the green gap problem, our calculations indicate that radiative recombination rates might significantly benefit from a reduced quantum-well-barrier-interface roughness.

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  • Received 17 April 2018
  • Revised 10 July 2018

DOI:https://doi.org/10.1103/PhysRevApplied.10.034027

© 2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Daniel S. P. Tanner, Joshua M. McMahon, and Stefan Schulz*

  • Photonics Theory Group, Tyndall National Institute, University College Cork, Cork T12 R5CP, Ireland

  • *stefan.schulz@tyndall.ie

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Vol. 10, Iss. 3 — September 2018

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