Title: Localization landscape theory of disorder in semiconductors. II. Urbach tails of disordered quantum well layers

Abstract

Urbach tails in semiconductors are often associated to effects of compositional disorder. The Urbach tail observed in InGaN alloy quantum wells of solar cells and LEDs by biased photocurrent spectroscopy is shown to be characteristic of the ternary alloy disorder. The broadening of the absorption edge observed for quantum wells emitting from violet to green (indium content ranging from 0% to 28%) corresponds to a typical Urbach energy of 20 meV. A three-dimensional absorption model is developed based on a recent theory of disorder-induced localization which provides the effective potential seen by the localized carriers without having to resort to the solution of the Schrodinger equation in a disordered potential. This model incorporating compositional disorder accounts well for the experimental broadening of the Urbach tail of the absorption edge. For energies below the Urbach tail of the InGaN quantum wells, type-II well-to-barrier transitions are observed and modeled. This contribution to the below-band-gap absorption is particularly efficient in near-ultraviolet emitting quantum wells. When reverse biasing the device, the well-to-barrier below-band-gap absorption exhibits a red-shift, while the Urbach tail corresponding to the absorption within the quantum wells is blue-shifted, due to the partial compensation of the internal piezoelectric fields by the externalmore » bias. The good agreement between the measured Urbach tail and its modeling by the localization theory demonstrates the applicability of the latter to compositional disorder effects in nitride semiconductors.« less

Authors:

Piccardo, Marco ^[1]; Li, Chi-Kang ^[2]; Wu, Yuh-Renn ^[2]; Speck, James S. ^[3]; Bonef, Bastien ^[3]; Farrell, Robert M. ^[3]; Filoche, Marcel ^[4]; Martinelli, Lucio ^[4]; Peretti, Jacques ^[4]; Weisbuch, Claude ^[1]

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+ Show Author Affiliations

1. Ecole Polytechnique, Univ. of Paris-Saclay, Palaiseau (France). Lab. of Condensed Matter Physics; Univ. of California, Santa Barbara, CA (United States). Dept. of Materials
2. National Taiwan Univ., Taipei (Taiwan). Graduate Inst. of Photonics and Optoelectronics and Dept. of Electrical Engineering
3. Univ. of California, Santa Barbara, CA (United States). Dept. of Materials
4. Ecole Polytechnique, Univ. of Paris-Saclay, Palaiseau (France). Lab. of Condensed Matter Physics

Publication Date:

Tue Apr 18 00:00:00 EDT 2017

Research Org.:

Univ. of California, Santa Barbara, CA (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Building Technologies Office; French National Research Agency (ANR); Ministry of Science and Technology (MOST), Taipei (Taiwan)

Contributing Org.:

Ecole Polytechnique Paris National Taiwan University

OSTI Identifier:

1429092

Alternate Identifier(s):

OSTI ID: 1352104; OSTI ID: 1635239

Grant/Contract Number:  

EE0007096; ANR-14-CE05-0048-01; MOST-104-2923-E-002-004-MY3; MOST-105-2221-E-002-098-MY3

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review. B

Additional Journal Information:

Journal Volume: 95; Journal Issue: 14; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 14 SOLAR ENERGY; 36 MATERIALS SCIENCE; disordered alloys; LEDs; nitrides; semiconductor compounds; optical absorption spectroscopy; Light emitting diodes, solid state lighting