Optical phonons of hexagonal and cubic GaN studied by infrared transmission and Raman spectroscopy

Giehler, M.; Ramsteiner, M.; Brandt, O.; Yang, Hee Chan; Ploog, K. H.

doi:10.1063/1.115208

Cited by 129 publications

(53 citation statements)

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“…For the model parameters, we used ε 0 = (ε 0 ε 2 0⊥ ) 1/3 = 9.79 [59], ε ∞ = (ε ∞ ε 2 ∞⊥ ) 1/3 = 5.5 [59], and ω LO = 92 meV [69]. ) points are denoted along the horizontal axis.…”

Section: Phonon Mode and Wave-vector Contributions To Phonon-assistedmentioning

confidence: 99%

First-principles calculations of indirect Auger recombination in nitride semiconductors

et al. 2015

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Auger recombination is an important nonradiative carrier recombination mechanism in many classes of optoelectronic devices. The microscopic Auger processes can be either direct or indirect, mediated by an additional scattering mechanism such as the electron-phonon interaction and alloy disorder scattering. Indirect Auger recombination is particularly strong in nitride materials and affects the efficiency of nitride optoelectronic devices at high powers. Here, we present a first-principles computational formalism for the study of direct and indirect Auger recombination in direct-band-gap semiconductors and apply it to the case of nitride materials. We show that direct Auger recombination is weak in the nitrides and cannot account for experimental measurements. On the other hand, carrier scattering by phonons and alloy disorder enables indirect Auger processes that can explain the observed loss in devices. We analyze the dominant phonon contributions to the Auger recombination rate and the influence of temperature and strain on the values of the Auger coefficients. Auger processes assisted by charged-defect scattering are much weaker than the phonon-assisted ones for realistic defect densities and not important for the device performance. The computational formalism is general and can be applied to the calculation of the Auger coefficient in other classes of optoelectronic materials.

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Section: Phonon Mode and Wave-vector Contributions To Phonon-assistedmentioning

confidence: 99%

First-principles calculations of indirect Auger recombination in nitride semiconductors

et al. 2015

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“…In hexagonal GaN the dominant Raman peak occurs at around 560 cm -1 , while the lines around 740 cm -1 are weaker. The 740 cm -1 has been observed in more recent works where, we believe, a cubic phase may have been present [1,7], and also in films with a low electron concentration. On the other hand, in cubic GaN the intense LO peak at about 740 cm -1 dominates and the forbidden TO peak at about 560 cm -1 is much weaker [1].…”

Section: εμ Góldys Et Almentioning

confidence: 73%

Morphology and Optical Properties of Laser-Assisted Chemical Vapour Deposited GaN

1998

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Properties of GaN epilayers grown by laser-assisted chemical vapour deposition are discussed. Good crystallinity and surface morphology of the films is demonstrated. Micro-Raman spectra are explained by scattering by small, randomly oriented cubic phase units present in the GaN film.PACS numbers: 68.55. 81.15.Gh, 61.16.Ch, Laser-assisted chemical vapour deposition (LCVD) has become an attractive technology in the electronic industry over the past decade. One of the key benefits of LCVD is that instead of using the thermal energy, LCVD takes advantage of photon energy to induce chemical reactions between reactants and deposit fllms. In this work we are using the photolytic process in which the ArF 193 nm excimer laser beam is absorbed by the precursor gases. The deposition of GaN was carried out at temperatures around 600°C. Low growth temperatures, between 470°C and 680°C, make possible the use of a range of thermally unstable substrates, such as silicon, gallium arsenide, quartz glass, in addition to sapphire and SiC.GaN films grown by LCVD with a range of ammonia flow rates show a systematic variation in electrical parameters. The Hall mobility increases proportionally with flow rate, from 55 cm 2 /(V s) to 90 cm 2 /(V s), saturating at 95 cm 2 /(V s) at flow rates above about 100 ml/min. The electron carrier concentration decreases monotonically and reproducibly from 10 17 cm -3 to 6 x 10 14 cm-3 over the flow rate range 0 to 100 ml/min. The sharp increase in the Hall mobility indicates that the electron scattering inside the film has been reduced. Nitrogen vacancies are therefore assumed to be reduced, as growth conditions are not changed other than by the addition of excess nitrogen via the ammonia plasma. Electron concentration continues to fall beyond mobility saturation, suggesting that the reduction in nitrogen vacancy concentration thought to be re8ponsible for large n-type autodoping, is accompanied by compensation, possibly by increasing the density of other defects caused by ion damage.(331)

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“…The position of the first peak fits with the wellknown LO phonon mode in GaAs. The line observed at 740 cm -1 corresponds to the LO phonon frequency in cubic GaN [22]. Recent experiments on Raman scattering in amorphous GaN 0.3 As 0.7 show a very broad weak feature around 750 cm -1 with FWHM of 280 cm -1 [23].…”

Section: Resultsmentioning

confidence: 99%

Optical Properties of GaNAs Grown by MBE

Pozina

Ivanov

Ḿonemar

et al. 1998

MRS Internet j. nitride semicond. res.

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Optical properties of the GaNxAs1−x layers grown on (001) GaAs substrates by molecular beam epitaxy have been studied. The samples can be classified into three categories with respect to the concentration of N, as determined by x-ray diffraction and secondary-ion mass spectrometry: (i) with doping nitrogen concentration, (ii) with average content of N less than 30 %, and (iii) with x close to 100 %. From optical measurements of photoluminescence and Raman scattering, combined with analysis of x-ray diffraction spectra, different phases are observed in the GaNxAs1−x layers: GaAs, GaN and the solid ternary solution GaNxAs1−x. We have estimated the fundamental band-gap energy in the GaNxAs1−x alloy with low nitrogen concentration (up to x = 0.04) from absorption measurements, and in GaNxAs1−x with low arsenic concentration (up to 1−x = 0.04) - from photoluminescence spectra. An analysis of the dependence of the experimental values of the GaNxAs1−x band-gap energy on the nitrogen composition indicates a constant bowing parameter b as large as b = -18 eV.

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Optical phonons of hexagonal and cubic GaN studied by infrared transmission and Raman spectroscopy

Cited by 129 publications

References 1 publication

First-principles calculations of indirect Auger recombination in nitride semiconductors

First-principles calculations of indirect Auger recombination in nitride semiconductors

Morphology and Optical Properties of Laser-Assisted Chemical Vapour Deposited GaN

Optical Properties of GaNAs Grown by MBE

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