Zone Edge Phonons in Gallium Phosphide

Pődör, B.

doi:10.1002/pssb.2221200123

Cited by 22 publications

(4 citation statements)

References 16 publications

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“…For example, in GaP the mobility above 400 K is limited by optical-mode scattering [13]. The Debye temperature is 580 K for the 12.06 THz LO mode of GaP [14]).…”

Section: Introductionmentioning

confidence: 99%

Calculating polaron mobility in halide perovskites

2017

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Lead halide perovskite semiconductors are soft, polar, materials. The strong driving force for polaron formation (the dielectric electron-phonon coupling) is balanced by the light band effectivemasses, leading to a strongly-interacting large-polaron. A first-principles prediction of mobility would help understand the fundamental mobility limits. Theories of mobility need to consider the polaron (rather than free-carrier) state due to the strong interactions. In this material we expect that at room temperature polar-optical phonon mode scattering will dominate, and so limit mobility. We calculate the temperature-dependent polaron mobility of hybrid halide perovskites by variationally solving the Feynman polaron model with the finite-temperature free-energies of Osaka. This model considers a simplified effective-mass band-structure interacting with a continuum dielectric of characteristic response frequency. We parametrise the model fully from electronicstructure calculations. In methylammonium lead iodide at 300 K we predict electron and hole mobilities of 133 and 94 cm 2 V −1 s −1 respectively. These are in acceptable agreement with singlecrystal measurements, suggesting that the intrinsic limit of the polaron charge carrier state has been reached. Repercussions for hot-electron photo-excited states are discussed. As well as mobility, the model also exposes the dynamic structure of the polaron. This can be used to interpret impedance measurements of the charge-carrier state. We provide the phonon-drag mass-renormalisation, and scattering time constants. These could be used as parameters for larger-scale device models and band-structure dependent mobility simulations.

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“…For example, in GaP the mobility above 400 K is limited by optical-mode scattering [13]. The Debye temperature is 580 K for the 12.06 THz LO mode of GaP [14]).…”

Section: Introductionmentioning

confidence: 99%

Calculating polaron mobility in halide perovskites

2017

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“…The features at energies below the α-line are identified as phonon replicas of the line and can be assigned to TA and TO/LO phonon modes based on the expected phonon energies from Raman characterization 10 and applying folding arguments to the ZB values. 16 , 17 The line labeled X is hidden as a shoulder in the unstrained NW spectrum but becomes more pronounced under strain. From temperature- and power-dependent characterization, the α, γ, and X lines were assigned to excitonic recombination.…”

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confidence: 99%

Optical Properties of Strained Wurtzite Gallium Phosphide Nanowires

et al. 2016

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Wurtzite gallium phosphide (WZ GaP) has been predicted to exhibit a direct bandgap in the green spectral range. Optical transitions, however, are only weakly allowed by the symmetry of the bands. While efficient luminescence has been experimentally shown, the nature of the transitions is not yet clear. Here we apply tensile strain up to 6% and investigate the evolution of the photoluminescence (PL) spectrum of WZ GaP nanowires (NWs). The pressure and polarization dependence of the emission together with a theoretical analysis of strain effects is employed to establish the nature and symmetry of the transitions. We identify the emission lines to be related to localized states with significant admixture of Γ7c symmetry and not exclusively related to the Γ8c conduction band minimum (CBM). The results emphasize the importance of strongly bound state-related emission in the pseudodirect semiconductor WZ GaP and contribute significantly to the understanding of the optoelectronic properties of this novel material.

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“…This energy difference is close to various longitudinal optical (LO) phonon energies in GaP, 50 meV at the C point, and about 46 meV at L and X valleys. 18 Hence, the second lower energy peak is from a phonon-assisted transition and the first peak is identified as the no-phonon (NP) peak. Note that the wider QWs have relatively weaker NP peaks.…”

Section: Experiments and Observationsmentioning

confidence: 99%

Light emission despite doubly-forbidden radiative transitions in AlP/GaP quantum wells: Role of localized states

Bhuyan

Mondal

Khatua

et al. 2013

Journal of Applied Physics

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Ammonia-molecular-beam epitaxial growth and optical properties of GaN/AlGaN quantum wells J. Appl. Phys. 91, 9685 (2002); 10.1063/1.1479756Localized quantum well excitons in InGaN single-quantum-well amber light-emitting diodesThe GaP/AlP/GaP heterostructure has an indirect gap both in real as well as momentum space, making the first order radiative recombination doubly forbidden. Nevertheless, we have observed relatively efficient emission from these structures. This paper comprehensively studies the origin of this improved light emission through a detailed analysis of the photoluminescence (PL) spectra. Our observations suggest that localized excitons within the acceptor states in GaP close to the heterostructure interface are enough for efficient light emission in these structures, doing away with the need for more complicated structures (superlattices or neighboring confinement structures). This real space localization of holes, close to the interface, apart from increasing the wave function overlap, also relaxes the delta-function momentum selection rule. Independent experimental evidence for this assertion comes from (i) the PL spectrum at high excitation power where transitions from both the localized as well as extended states are independently observed, (ii) the observation that extended states emission has the expected band-bending-induced blue-shift with increase in excitation power, whereas the localized states do not, (iii) observation of phonon replicas for PL from localized states, and (iv) observation of persistent photoconductivity at low temperature. Finally, we propose a simple analytical model that accounts for both the type-II nature as well as the indirect bandgap to explain the improvement of radiative recombination efficiency with increased localization. The experimental observations are reproduced within an order of magnitude. The model is very general and it also provides a framework to study the optical properties of other such (type-II and/or indirect gap) heterostructures. V C 2013 AIP Publishing LLC. [http://dx.

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Zone Edge Phonons in Gallium Phosphide

Cited by 22 publications

References 16 publications

Calculating polaron mobility in halide perovskites

Calculating polaron mobility in halide perovskites

Optical Properties of Strained Wurtzite Gallium Phosphide Nanowires

Light emission despite doubly-forbidden radiative transitions in AlP/GaP quantum wells: Role of localized states

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