Phonon Sidebands Research Articles

Structural features and photoluminescence behaviors of color-temperature tunable (Gd,Y)3Al5O12:Ce3+/Cr3+ phosphors with varying compositions

We designed a chemical coprecipitation method to obtain hollow round precursors with hydrated basic carbonate sulfate structures; these precursors were then thermally treated to yield near-spherical (Gd0.99-xYxCe0.01)3(Al1-yCry)5O12 (x = 0.25‒0.99, y = 0‒0.02) garnet phosphors. With ≥35 at.% Y3+ substitution for Gd3+, relatively stable garnet crystal structures could be obtained. More Y3+ addition led to shrinkage of the unit cell; however, Cr3+ doping caused crystal lattice expansion. The Ce3+ activated phosphor exhibited a strong broad emission band at 500‒700 nm arising from 2D3/2→ 2F5/2,7/2 transitions of Ce3+, while the Cr3+ codoped sample presented three additional red emission bands in the range of 675‒725 nm arrtibuted to 2Eg (2g) →4A2g (4f) transition of Cr3+ and some phonon sidebands. At a constant Ce3+ content of 1 at.%, the Cr3+ emission intensity increased to maximum at 0.5 at.% Cr3+ concentration via efficient energy transfer from Ce3+ to Cr3+, which was attributed to electric multipole interactions such as dipole-quadrupole interactions. A higher particle calcination temperature significantly enhanced the luminescence intensity as well as caused spectral redshifts via correlation-induced enhancement of the crystal field splitting. The color temperature could be tailored in a wide range of ∼5075‒3374 K by controlling both Y3+/Gd3+ ratio and calcination temperature. The Cr3+ addition further shortened the fluorescence lifetime for the 556 nm emission of Ce3+.

Structural and luminescence characterization of europium-doped niobium germanate glasses and glass-ceramics: Novel insights from 93Nb solid-state NMR spectroscopy

A thorough understanding of network former roles in optical glasses and glass-ceramics, as well as structural environments of luminescent rare-earth atoms, is paramount to assessing their suitability and effectiveness as components for fully-optical integrated devices. The present contribution sheds light on the overall poorly understood structural role of Nb2O5 in oxide glasses and offers a rationale for the luminescence changes concomitant to the heat-treatment induced glass-to-crystal transition in niobium germanate glasses. To this end, results from 93Nb nuclear magnetic resonance (NMR), Raman, and Eu3+ ion based luminescence spectroscopies as well as 3D micromanufacturing are reported for glasses and glass-ceramics in system (89.9-x)GeO2-xNb2O5-10K2O-0.1Eu2O3. Thanks to very-fast 93Nb magic-angle spinning (MAS) and a novel excitation scheme for Triple-quantum (TQ)MAS solid-state NMR spectroscopy distinct Nb(OGe)6-y(ONb)y species were identified for the first time: at low Nb concentrations structural units with rather low y-values are formed, reaching down to isolated Nb(OGe)6 units – next to units bearing non-bridging oxygen atoms; at intermediate Nb contents and beyond, structural units with increasingly higher y-values up to Nb(ONb)6 are found, resembling the local environments found in crystalline Nb2O5. After the glass-to-crystal transition the Nb local environment maintains a high degree of disorder while some residual glass remains. Moreover, photoluminescence spectroscopy of the europium probes suggests the rare-earth ions are preferentially incorporated into high y-value Nb(OGe)6-y(ONb)y polyhedra based on spectral features such as the phonon sideband, the 5D0 → 7F2/7F1 ratio, and split 4f bands. Finally, femtosecond laser microfabrication of waveguides was successful in the presented europium-doped niobium germanate glasses, making them promising candidates for further studies as photonic devices.

Complete Mapping of Interacting Charging States in Single Coupled Colloidal Quantum Dot Molecules

Colloidal quantum dots (CQDs), major building blocks in modern optoelectronic devices, have so far been synthesized with only one emission center where the exciton resides. Recent development of coupled colloidal quantum dots molecules (CQDM), where two core–shell CQDs are fused to form two emission centers in close proximity, allows exploration of how charge carriers in one CQD affect the charge carriers in the other CQD. Cryogenic single particle spectroscopy reveals that while CQD monomers manifest a simple emission spectrum comprising a main emission peak with well-defined phonon sidebands, CQDMs exhibit a complex spectrum with multiple peaks that are not all spaced according to the known phonon frequencies. Based on complementary emission polarization and time-resolved analysis, this is assigned to fluorescence of the two coupled emission centers. Moreover, the complex peak structure shows correlated spectral diffusion indicative of the coupling between the two emission centers. Utilizing Schrödinger-Poisson self-consistent calculations, we directly map the spectral behavior, alternating between neutral and charged states of the CQDM. Spectral shifts related to electrostatic interaction between a charged emission center and the second emission center are thus fully mapped. Furthermore, effects of moving surface charges are identified, whereby the emission center proximal to the charge shows larger shifts. Instances where the two emission centers are negatively charged simultaneously are also identified. Such detailed mapping of charging states is enabled by the coupling within the CQDM and its anisotropic structure. This understanding of the coupling interactions is progress toward quantum technology and sensing applications based on CQDMs.

Sub-bandgap photoluminescence properties of multilayer h-BN-on-sapphire

Two-dimensional hexagonal boron nitride (h-BN) materials have garnered increasing attention due to its ability of hosting intrinsic quantum point defects. This paper presents a photoluminescence (PL) mapping study related to sub-bandgap-level emission in bulk-like multilayer h-BN films. Spatial PL intensity distributions were carefully analyzed with 500 nm spatial resolution in terms of zero phonon line (ZPL) and phonon sideband (PSB) emission-peaks and their linewidths, thereby identifying the potential quantum point defects within the films. Two types of ZPL and PSB emissions were confirmed from the point defects located at the non-edge and edge of the films. Our statistical PL data from the non-edge- and edge-areas of the sample consistently reveal broad and narrow emissions, respectively. The measured optical properties of these defects and the associated ZPL peak shift and line broadening as a function of temperature between 77° and 300° K are qualitatively and quantitatively explained. Moreover, an enhancement of the photostable PL emission by at least a factor of ×3 is observed when our pristine h-BN was irradiated with a 532 nm laser.

Many-body Green's function approaches to the doped Fröhlich solid: Exact solutions and anomalous mass enhancement

In polar semiconductors and insulators, the Fr\"ohlich interaction between electrons and long-wavelength longitudinal optical phonons induces a many-body renormalization of the carrier effective masses and the appearence of characteristic phonon sidebands in the spectral function, commonly dubbed 'polaron satellites'. The simplest model that captures these effects is the Fr\"ohlich model, whereby electrons in a parabolic band interact with a dispersionless longitudinal optical phonon. The Fr\"ohlich model has been employed in a number of seminal papers, from early perturbation-theory approaches to modern diagrammatic Monte Carlo calculations. One limitation of this model is that it focuses on undoped systems, thus ignoring carrier screening and Pauli blocking effects that are present in real experiments on doped samples. To overcome this limitation, we here extend the Fr\"ohlich model to the case of doped systems, and we provide exact solutions for the electron spectral function, mass enhancement, and polaron satellites. We perform the analysis using two approaches, namely Dyson's equation with the Fan-Migdal self-energy, and the second-order cumulant expansion. We find that these two approaches provide qualitatively different results. In particular, the Dyson's approach yields better quasiparticle masses and worse satellites, while the cumulant approach provides better satellite structures, at the price of worse quasiparticle masses. Both approaches yield an anomalous enhancement of the electron effective mass at finite doping levels, which in turn leads to a breakdown of the quasiparticle picture in a significant portion of the phase diagram.

Optically detected magnetic resonance of nitrogen-vacancy centers in vertical diamond Schottky diodes

Diamond solid-state devices are very attractive to electrically control the charge state of nitrogen-vacancy (NV) centers. In this work, p-type vertical diamond Schottky diodes (VDSDs) are introduced as a platform to electrically control the interconversion between the neutral charge NV (NV0) and negatively charged NV (NV−) centers. The photoluminescence of NV centers generated by ion implantation in VDSDs shows an increase in NV− zero phonon line (ZPL) and phonon sideband intensities with reverse voltage, whereas the NV0 ZPL intensity decreases. Thus, NV centers embedded in VDSDs are converted into NV− under reverse bias voltage. Moreover, the optically detected magnetic resonance (ODMR) of NV− exhibits an increase in the ODMR contrast with reverse bias voltage and splitting of the resonance dips. Since no magnetic field is applied, the dip splitting in the ODMR spectrum is ascribed to the Stark effect induced by the interaction of NV− with the electric field existing within the depletion region of VDSDs.

Structural characterization, Gd3+ → Eu3+ energy transfer and radiative properties of Gd/Eu in codoped Li2O–ZnO–SrO–B2O3–P2O5 glass

A series of Gd doped Li2O–ZnO–SrO–B2O3–P2O5 glasses and co-doped samples with different Eu3+ concentrations was synthesized through the conventional melt quenching route. The structural, morphological, and elemental distributions were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray analysis. The effect of Gd doping on the thermal properties of prepared glasses was studied by differential thermal analysis. Characteristics photoluminescence (PL) emissions of Gd3+ (6P7/2→8SJ/2) and Eu3+ (5D0→7FJ) were observed in the doped glass matrix. Strong PL emissions at 312 nm (6P7/2 → 8S7/2) shown by the Gd-doped glasses upon excitation at 274 nm suggests its prospect in phototherapy applications. Phonon energy of the glass matrix calculated from the phonon sidebands of Eu3+ spectra was obtained as 970 cm−1. The values of branching ratios and stimulated emission cross-sections obtained from Judd-Ofelt analysis indicate the suitability of the prepared Gd–Eu co-doped glasses for optical display devices. The Observed Ω2 > Ω4 suggests Eu3+ occupancy preferably at less centrosymmetric sites in the studied glass hosts. The change in the local symmetry environment of the dopant ions with Gd incorporation was further analyzed by determining the asymmetry ratio of Eu3+ emission in the co-doped glass. The emission spectra and luminescence lifetimes suggested the efficient energy transfer from Gd3+ to Eu3+. Co-doping of Gd led to better chromaticity values and improved color purity of Eu3+ red emission.

Optical transition properties, internal quantum efficiencies, and temperature sensing of Er3+ doped BaGd2O4 phosphor with low maximum phonon energy

AbstractThe hosts with low maximum phonon energy (MPE) are preferred since the nonradiative consumption of the luminescence centers in them are low. Among the low MPE hosts, the oxide ones are more favored owing to their excellent stability and easy synthesis. In this work, the optical and spectroscopic properties of BaGd2O4:Er3+ phosphor were studied. The MPE of BaGd2O4 host was observed from Eu3+ phonon sideband (PSB) spectrum and Raman spectrum to be 477 cm−1 which does not second to the fluoride hosts. The refractive index, which is indispensable for Judd–Ofelt calculation, was confirmed from the both approaches of the Eu3+‐probe and the band gap energy, and the similar refractive indices were confirmed, therefore the average refractive index 2.01 was used in the Judd–Ofelt calculation. The Judd–Ofelt parameters of Er3+ in BaGd2O4 host was confirmed to be = 7.91 × 10−21 cm2, = 2.36 × 10−21 cm2, and = 9.00 × 10−22 cm2. Furthermore, the internal quantum efficiencies for 4F9/2 and 4IJ (J = 9/2, 11/2, and 13/2) levels were determined. Finally, the optical temperature sensing properties were studied in detail, and the temperature calibration curve was experimentally derived, meanwhile the maximum absolute sensitivity was confirmed to be 0.0028 K−1.

Investigation of the TeO2/GeO2 Ratio on the Spectroscopic Properties of Eu3+-Doped Oxide Glasses for Optical Fiber Application.

This study presented an analysis of the TeO2/GeO2 molar ratio in an oxide glass system. A family of melt-quenched glasses with the range of 0–35 mol% of GeO2 has been characterized by using DSC, Raman, MIR, refractive index, PLE, PL spectra, and time-resolved spectral measurements. The increase in the content of germanium oxide caused an increase in the transition temperature but a decrease in the refractive index. The photoluminescence spectra of europium ions were examined under the excitation of 465 nm, corresponding to 7F0 → 5D2 transition. The PSB (phonon sidebands) analysis was carried out to determine the phonon energy of the glass hosts. It was reported that the red (5D0 → 7F2) to orange (5D0 → 7F1) fluorescence intensity ratio for Eu3+ ions decreased from 4.49 (Te0Ge) to 3.33 (Te15Ge) and showed a constant increase from 4.58 (Te20Ge) to 4.88 (Te35Ge). These optical features were explained in structural studies, especially changes in the coordination of [4]Ge to [6]Ge. The most extended lifetime was reported for the Eu3+ doped glass with the highest content of GeO2. This glass was successfully used for the drawing of optical fiber.

High-resolution spectroscopy of neutral Yb atoms in a solid Ne matrix

We present an experimental and theoretical study of the absorption and emission spectra of Yb atoms in a solid Ne matrix at a resolution of 0.025 nm. Five absorption bands were identified as due to transitions from the $4{f}^{14}5{d}^{0}6{s}^{2}{\phantom{\rule{4pt}{0ex}}}^{1}{S}_{0}$ ground-state configuration to $4{f}^{14}5{d}^{0}6s6p$ and $4{f}^{13}5{d}^{1}6{s}^{2}$ configurations. The two lowest-energy bands were assigned to outer-shell transitions to $6s6p{\phantom{\rule{4pt}{0ex}}}^{3}{P}_{1}$ and ${}^{1}{P}_{1}$ atomic states and displayed the structure of a broad doublet and an asymmetric triplet, respectively. The remaining three higher-frequency bands were assigned to inner-shell transitions to distinct $J=1$ states arising from the $4{f}^{13}5{d}^{1}6{s}^{2}$ configuration and were highly structured with narrow linewidths. A classical simulation was performed to identify the stability and symmetry of possible trapping sites in the Ne crystal. It showed that the overarching $1+2$ structure of the high-frequency bands could be predominantly ascribed to crystal-field splitting in the axial field of a 10-atom vacancy of ${C}_{4v}$ symmetry. Their prominent substructures were shown to be manifestations of phonon sidebands associated with the zero-phonon lines on each crystal-field state. Unprecedented for a metal--rare-gas system, resolution of individual phonon states on an allowed electronic transition was possible under excitation spectroscopy which reflects the semiquantum nature of solid Ne. In contrast to the absorption spectra, emission spectra produced by steady-state excitation into the ${}^{1}{P}_{1}$ absorption band consisted of simple, unstructured fluorescence bands.

Ultraintense Zero-Phonon Line from a Mn4+ Red-Emitting Phosphor for High-Quality Backlight Display Applications.

The zero-phonon line (ZPL) of Mn4+, which highly depends on its local environment, is usually much weaker than the vibrational phonon sidebands. In this work, an ultraintense ZPL emission, coming from a brand new red-emitting Rb2LiGaF6:Mn4+ (RLGFM) phosphor upon blue light excitation, is presented. The interesting spectral characteristic originates from the nonequivalent substitution of Mn4+ for Ga3+ in a rigid octahedral structure with a low symmetry, which induces neighboring cation vacancies that distort the local symmetry of the [MnF6] octahedra. Benefiting from the ultraintense ZPL emission, a wide color gamut is achieved using RLGFM and β-SiAlON:Eu2+ as color converters. Moreover, a comprehensive investigation on the thermal quenching behavior is also conducted to provide detailed insights to explore novel Mn4+ red phosphors for high-quality backlight display applications.

High-Pressure Photoluminescence Properties of Cr3+-Doped LaGaO3 Perovskites Modulated by Pressure-Induced Phase Transition.

The photoluminescence properties of Cr3+-doped LaGaO3 perovskites are investigated by high-pressure spectroscopy. The pressure-induced phase transition from orthorhombic (Pbnm) to rhombohedral (R3̅c) at around 2 GPa is confirmed by Raman spectroscopy. Cr3+-doped LaGaO3 shows deep-red emission peaks around 730 nm due to the zero-phonon line (R-line) and the phonon sidebands, which correspond to Cr3+: 2Eg → 4A2g transitions in the ideal octahedral site and the Cr-Cr pair luminescence (N-line) under ambient condition. Under a high pressure, the R-line shifts to a lower energy at a rate of -13 cm-1/GPa. From the pressure dependence of photoluminescence excitation (PLE) spectra, it is suggested that the redshift of the R-line is caused by the decrease of Racah parameters B and C. Moreover, the N-line luminescence becomes stronger relative to the R-line with increasing pressure and the N-line/R-line can be used to monitor the phase transition pressure. Under a high pressure, the tilt angle of the GaO6 octahedral unit becomes smaller. It implies that the enhanced N-line luminescence is caused by the stronger superexchange interaction between Cr3+ ions due to the increased Cr-O-Cr bond angle closer to 180°.

Crystallization of bronze-like perovskite in potassium tantalum germanate glasses: Glass ceramic preparation and its optical properties

Structural, optical and photoluminescent properties of Europium-doped potassium germanate glassy materials were investigated in terms of tantalum content and nanoscale crystallization of potassium tantalate K2Ta8O21. For such purpose, an Eu3+-doped germanate glass, Eu3+-doped tantalum germanate glass and Eu3+-doped tantalum germanate glass-ceramics were prepared and characterized by X-ray diffraction, Raman, UV–Vis–NIR and photoluminescence spectroscopies. Eu3+ emission properties were used as a sensitive probe to investigate its symmetry site into the host structure. The chemical microenvironment around Eu3+ ions have changed with tantalum concentration as well as bronze-like tantalum perovskite K2Ta8O21 phase crystallization into the glasses. The ions preferably occupy sites of higher symmetry and lower energy phonons, which attest the ions migration to the tantalum-rich crystalline environment. The correlation between the phonon side band (PSB) spectra and Raman vibrational modes, 5D0 → 7F2/5D0 → 7F1 ratio and experimental Eu3+5D0 lifetime support this assumption. The highest photoluminescence intrinsic quantum yield (QEuEu) is calculated for glass-ceramics heat-treated for 20 h by using Judd-Ofelt theory, indicating reduction of nonradiative decay processes due to the lower local phonon energy. The luminescence quenching for longer crystallization times demonstrates the importance of optimizing thermal treatment parameters to ensure proper distance between optically active ions. Accordingly, tantalum germanate glass-ceramics are promising for photonic devices as red laser, solid-state lighting and energy conversion applications, as well as for nonlinear optical applications considering the perovskite bronze-like crystallization.

Optical properties of Praseodymium (Pr3+) doped bismuth boro-tellurite glasses containing CdSe nanoparticles

Adding TeO2 and growing nanoparticles of CdSe can significantly affect the optical properties of Pr3+ ions doped in bismuth borate glasses. We used a modified Judd-Ofelt analysis to obtain the intensity parameters from the optical absorption spectra. Adding TeO2 leads to an increase in the covalency of the Pr-O bond. However, the presence of CdSe nanoparticles makes Pr-O bond less covalent. Optical band gap shows a considerable decrease when nanoparticles are present. Phonon side band analysis suggests that energy levels of Pr3+ responsible for the intense red emission are populated through a cross-relaxation mechanism instead of multiphonon decay process. The blue transition of Pr3+ shows significant enhancement for the stimulated emission cross-section when CdSe nanoparticles are present. Chromaticity analysis identifies the overall light emissions from different glass samples with various standard sources. Our glass samples also possess high spectroscopic quality factors compared to similar systems doped with Pr3+ ions.

Spectral asymmetry of phonon sideband luminescence in monolayer and bilayer WSe2

We report an experimental study of temperature-dependent spectral line shapes of phonon sideband emission stemming from dark excitons in monolayer and bilayer WSe2. Using photoluminescence spectroscopy in the range from 4 to 100 K, we observe a pronounced asymmetry in the phonon-assisted luminescence from momentum-indirect exciton reservoirs. We demonstrate that the corresponding spectral profiles are distinct from those of bright excitons with direct radiative decay pathways. The line-shape asymmetry reflects thermal distribution of exciton states with finite center-of-mass momenta, characteristic for phonon sideband emission. The extracted temperature of the exciton reservoirs is found to generally follow that of the crystal lattice, with deviations reflecting overheated populations. The latter are most pronounced in the bilayer case and at lowest temperatures. Our results add to the understanding of phonon-assisted recombination of momentum-dark excitons and, more generally, establish means to access the thermal distribution of finite-momentum excitons in atomically thin semiconductors with indirect band gaps.Received 21 May 2021Revised 28 September 2021Accepted 30 September 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.L042019Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasExcitonsPhysical SystemsTransition metal dichalcogenidesTechniquesPhotoluminescenceCondensed Matter, Materials & Applied Physics

Spin Polarization, Electron-Phonon Coupling, and Zero-Phonon Line of the NV Center in 3C-SiC.

The nitrogen-vacancy (NV) center in 3C-SiC, the analog of the NV center in diamond, has recently emerged as a solid-state qubit with competitive properties and significant technological advantages. Combining first-principles calculations and magnetic resonance spectroscopy, we provide thorough insight into its magneto-optical properties. By applying resonantly excited electron paramagnetic resonance spectroscopy, we identified the zero-phonon absorption line of the 3A2 → 3E transition at 1289 nm (within the telecom O-band) and measured its phonon sideband, the analysis of which reveals a Huang-Rhys factor of S = 2.85 and a Debye-Waller factor of 5.8%. The low-temperature spin-lattice relaxation time was found to be exceptionally long (T1 = 17 s at 4 K). All these properties make NV in 3C-SiC a strong competitor for qubit applications. In addition, the strong variation of the zero-field splitting in the range 4-380 K allows its application for nanoscale thermal sensing.

Nonequilibrium resonant inelastic x-ray scattering study of an electron-phonon model

We use the nonequilibrium dynamical mean field theory formalism to compute the equilibrium and nonequilibrium resonant inelastic X-ray scattering (RIXS) signal of a strongly interacting fermionic lattice model with a coupling of dispersionless phonons to the total charge on a given site. In the atomic limit, this model produces phonon subbands in the spectral function, but not in the RIXS signal. Electron hopping processes however result in phonon-related modifications of the charge excitation peak. We discuss the equilibrium RIXS spectra and the characteristic features of nonequilibrium states induced by photo-doping and by the application of a static electric field. The latter produces features related to Wannier-Stark states, which are dressed with phonon sidebands. Thanks to the effect of field-induced localization, the phonon features can be clearly resolved even in systems with weak electron-phonon coupling.

Resonance-fluorescence spectral dynamics of an acoustically modulated quantum dot

Quantum technologies that rely on photonic qubits require a precise controllability of their properties. For this purpose hybrid approaches are particularly attractive because they offer a large flexibility to address different aspects of the photonic degrees of freedom. When combining photonics with other quantum platforms like phonons, quantum transducers have to be realized that convert between the mechanical and optical domain. Here, we realize this interface between phonons in the form of surface acoustic waves (SAWs) and single photons, mediated by a single semiconductor quantum dot exciton. In this combined theoretical and experimental study, we show that the different sidebands exhibit characteristic blinking dynamics that can be controlled by detuning the laser from the exciton transition. By developing analytical approximations we gain a better understanding of the involved internal dynamics. Our specific SAW approach allows us to reach the ideal frequency range of around 1 GHz that enables simultaneous temporal and spectral phonon sideband resolution close to the combined fundamental time-bandwidth limit.

Thermal Properties of Red Zero-Phonon Luminescence Line from Mn2+ Ions in Oxide Crystals

Temperature dependence of emission properties of sharp, zero-phonon line (ZPL) associated with 4T1g →6A1g transition of Mn2+ ions doped in LiMgPO4 is studied, together with the Mn2+-concentration dependence. The ZPL is observed at 611.8 nm at temperatures below 120 K. The intensity relative to the intensity of superimposed phonon sidebands is increased in proportion to T2 with increasing temperature from 18 K. The peak energy and full width at half maximum (FWHM) are increased in proportion to coth 1/2 (hν/2kBT). Unlike the phonon sideband emission which shows single exponential decay and decrease of decay time with increase of temperature, the ZPL emission has the fast and slow decay components and shows temperature-independent decay times. A blue shift of the ZPL peak energy is observed with increase of Mn2+ concentration x doped in LiMg1−x Mn x PO4 from 0.0015 to 0.0050 at 18 K, while a broadening of line width is observed with increase of the concentration. Each of the peak energy and FWHM is approximated by a quadratic equation in the form a+bx+cx 2. It is suggested that these results are understood by the interaction of the excited 4T1g state with phonons and crystal field, from comparison with the theoretically expected formulae.

Phonon sidebands of the optical spectrum for the defect structure GaN:C +O

We investigate the multi-phonon sidebands of the optical spectra of point defects in GaN based on the Huang-Rhys model, in which the localized phonon modes and the reorganization energy associated with the defect structure GaN: C N + O N are precisely calculated by ab initio approach. We present multi-phonon sidebands for both the localized phonon modes and intrinsic longitudinal optical phonon modes and give the comparisons between them in detail. Meanwhile, different types of the combinational phonon sidebands that are consisted of two localized phonon modes with different proportions are proposed. These multi-phonon sidebands not only could be used for the analysis of fine structure of the optical spectra, but also served as the fingerprints for the defect structures. • Multi-phonon sidebands of the optical spectra for point defects in GaN are present. • Localized phonon modes associated with the defect structure are calculated by ab initio approach. • Multi-phonon sidebands could be served as the fingerprints for the defect structures.