Electron–phonon effects on the direct band gap in semiconductors: LCAO calculations

Olguı́n, D.; Cardona, M.; Cantarero, A.

doi:10.1016/s0038-1098(02)00225-9

Cited by 66 publications

(41 citation statements)

References 66 publications

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“…6.44 of [14]. An average renormalization value of -62 meV has been calculated by LCAO techniques in [17]. This gap exhibits a spin-orbit splitting ∆ 0 and the corresponding isotope effect has been measured for both components, E 0 and E 0 +∆ 0 [41].…”

Section: Absorption Edges Of Germanium and Siliconmentioning

confidence: 93%

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Electron–phonon interaction in tetrahedral semiconductors

Cardona

2005

Solid State Communications

160

141

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Considerable progress has been made in recent years in the field of ab initio calculations of electronic band structures of semiconductors and insulators. The oneelectron states (and the concomitant two-particle excitations) have been obtained without adjustable parameters, with a high degree of reliability. Also, more recently, the electron-hole excitation frequencies responsible for optical spectra have been calculated. These calculations, however, are performed with the constituent atoms fixed in their crystallographic positions and thus neglect the effects of the lattice vibrations (i.e. electron-phonon interaction) which can be rather large, even larger than the error bars assumed for ab initio calculations.Effects of electron-phonon interactions on the band structure can be experimentally investigated in detail by measuring the temperature dependence of energy gaps or critical points (van Hove singularities) of the optical excitation spectra. These studies have been complemented in recent years by observing the dependence of such spectra on isotopic mass whenever different stable isotopes of a given atom are available at affordable prices. In crystals composed of different atoms, the effect of the vibration of each separate atom can thus be investigated by isotopic substitution. Because of the zero-point vibrations, such effects are present even at zero temperature (T = 0).In this paper we discuss state-of-the-art calculations of the dielectric function spectra and compare them with experimental results, with emphasis on the differences introduced by the electron-phonon interaction. The temperature dependence of various optical parameters will be described by means of one or two (in a few cases three) Einstein oscillators, except at the lowest temperatures where the T 4 law (contrary to the Varshni T 2 result) will be shown to apply. Increasing an isotopic mass increases the energy gaps, except in the case of monovalent Cu (e.g., CuCl) and possibly Ag (e.g., AgGaS 2 ). It will be shown that the gaps of tetrahedral materials containing an element of the first row of the periodic table (C,N,O) are strongly affected by the electron-phonon interaction. It will be conjectured that this effect is related to the superconductivity recently observed in heavily boron-doped carbon.

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Section: Absorption Edges Of Germanium and Siliconmentioning

confidence: 93%

“…1) [16,17]. The present article is concerned with the temperature dependent shifts induced in the critical point energies by the electron-phonon interaction and their broadenings, which correspond to the imaginary part of the interaction selfenergy [18].…”

Section: Effect Of Electron-phonon Interaction On Electronic States Amentioning

confidence: 99%

Electron–phonon interaction in tetrahedral semiconductors

Cardona

2005

Solid State Communications

160

141

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“…(iii) Renormalization of the electron energy due to the EPI is usually much smaller than the dominant energy scale in our study, which is the energy bandgap. Experimental measurement [61] and first-principles calculation [62] found that the renormalization of bandgap in GaAs is only about 0.04 eV. We also note that without considering this electron energy renormalization mediated by EPI, people have shown reasonable electron scattering rates for GaAs [49] and TiO 2 [50], and therefore our treatment here by ignoring the electron renormalization due to electron-phonon interaction should be good enough for the transport properties, which is also confirmed by the calculated mobility compared with experiments.…”

Section: Limitations Of Presented First-principles Frameworkmentioning

confidence: 99%

First-principles mode-by-mode analysis for electron-phonon scattering channels and mean free path spectra in GaAs

et al. 2017

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We present a first-principles framework to investigate the electron scattering channels and transport properties for polar materials by combining the exact solution of linearized electronphonon (e-ph) Boltzmann transport equation in its integral-differential form associated with the e-ph coupling matrices obtained from polar Wannier interpolation scheme. No ad hoc parameter is required throughout this calculation, and GaAs, a well-studied polar material, is used as an example to demonstrate this method. In this work, the long-range and short-range contributions as well as the intravalley and intervalley transitions in the e-ph interactions (EPIs) have been quantitatively addressed. Promoted by such mode-by-mode analysis, we find that in GaAs, the piezoelectric scattering is comparable to deformation-potential scattering for electron scatterings by acoustic phonons in EPI even at room temperature and makes a significant contribution to mobility. Furthermore, we achieved good agreement with experimental data for the mobility, and identified that electrons with mean free paths between 130 and 210 nm provide the dominant contribution to the electron transport at 300 K. Such information provides a deeper understanding on the electron transport in GaAs, and the presented framework can be readily applied to other polar materials.

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“…The temperature dependence of the bandgap energy has two contributions: the thermal lattice dilatation, which causes an increase and the electronphonon coupling, which causes a decrease of the bandgap energy with temperature. [21] Classical semiconductors, e.g., GaAs and Si, typically exhibit a redshift of the bandgap due to enhanced electron-phonon coupling with increasing temperature. In contrast to that, the bandgap energy of MAPbI 3 in the tetragonal phase has a positive temperature coefficient, i.e., it shifts to the blue spectral range with increasing temperature.…”

Section: Absorptionmentioning

confidence: 99%

Impact of Structural Dynamics on the Optical Properties of Methylammonium Lead Iodide Perovskites

Panzer

Meier

et al. 2017

Advanced Energy Materials

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structure, [2] and changing the ratio of precursor compounds prior to the formation of the perovskite layer. [3] These approaches are based on modifying the crystallization process, for example, by controlling the composition of the precursor solution and by varying processing parameters. Such changes also led to major improvements in perovskite-based light-emitting devices within the last year. Initially, the current efficiencies were improved by optimizing the grain size to values below 100 nm, and by changing the precursor compound molar proportions. [4] More recently, efficient perovskite-based LEDs with external quantum efficiencies exceeding 10% were even obtained by expanding towards lower dimensional perovskite structures. [5] Different structures and dimensionalities resulted in altered charge-carrier dynamics affecting the radiative recombination efficiency. [5,6] By drawing strong correlations between structural properties and their electronic structure, major breakthroughs toward light-emitting devices or in photovoltaics could be achieved in very recent years. To a certain extent, this resembles the evolution in the field of organic semiconductors, where improved understanding of the interplay between morphological and electronic structure proved essential to facilitate the recent progress in organic photovoltaics, and the successful commercialisation of organic LED devices. Also, for hybrid perovskites the question of how crystal structure, shape, and grain size governs the electronic structure will remain an important topic in the future to further improve perovskite-based optoelectronic devices. Since the solution processability of hybrid perovskites enables easy tuning of material compositions, a large number of different hybrid perovskites were reported. For example, exchanging the organic cation can alter the crystal structure, shift phase transitions, as does formamidinium, or change further excited-state dynamics, as is happening with Cs or Ru. Furthermore, different halide anions change the optical and excited state properties. The optical bandgap can be changed from the UV to NIR region by replacing the halide from Cl to Br to I. Mixed-halide systems thereof even provide a way to gradually tune the respective bandgap. In fact, the recently reported, most stable and efficient perovskite solar cells (PSCs) are based on a highly optimized mixture of different anions and cations. [1,7] Nevertheless, the most investigated hybrid perovskite representative is the methylammonium lead iodide perovskite CH 3 NH 3 PbI 3 (MAPbI 3 ), which, in the meantime, has become Organolead halide perovskites have attracted a lot of attention over the recent years mostly due to their bright prospective application in photovoltaic devices. For further development, characterization of their physical properties plays a seminal role in order to gain an in-depth understanding of these mid-bandgap ionic semiconductors. Their unique optical and electronic properties are a result of their characteristic electronic stru...

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Electron–phonon effects on the direct band gap in semiconductors: LCAO calculations

Cited by 66 publications

References 66 publications

Electron–phonon interaction in tetrahedral semiconductors

Electron–phonon interaction in tetrahedral semiconductors

First-principles mode-by-mode analysis for electron-phonon scattering channels and mean free path spectra in GaAs

Impact of Structural Dynamics on the Optical Properties of Methylammonium Lead Iodide Perovskites

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