Optical phonon behavior in strain-free dilute Ga(As,N) studied by Raman scattering

Self Cite

We investigate inelastic light scattering by longitudinal optic phonon-plasmon coupled modes ͑LOPCMs͒ in a series of heavily Se-doped, n-type GaAs 1−x N x epilayers with x Ͻ 0.4%. We perform a line shape analysis of the LOPCM spectra to estimate the optical effective mass, m opt ‫ء‬ , and the scattering time of the conduction electrons in GaAsN. We use these results to evaluate an effective carrier mobility for our samples. The values thus obtained, which we compare with measured electron Hall mobilities, indicate that the x-dependence of the mobility in GaAs 1−x N x is dominated by the scattering time, rather than by the variation of the electron effective mass. The Raman analysis yields m opt ‫ء‬ values that are lower than those obtained from the band anticrossing model.

Section: Methodsmentioning

confidence: 99%

“…14 The broad band centered at ϳ268 cm −1 can be assigned to the GaAs-like TO mode of GaAsN. 26,27 An additional broad feature that is not observed in undoped GaAsN and whose frequency and width change from sample to sample emerges between the TO and LO GaAs-like phonons. We assign this feature to a heavily damped LOPCM.…”

Section: Methodsmentioning

confidence: 99%

Electron effective mass and mobility in heavily doped n-GaAsN probed by Raman scattering

Ibáñez

Cuscó

Alarcón-Lladó

et al. 2008

Self Cite

“…Phonon frequencies are strongly dependent on any strain present in the GaAs-based alloys. [22][23][24][25][26] Such stress-induced shifts can be essentially explained by the phonon deformation potentials (PDPs). Detailed expressions for PDPs and their consequences for the first-order Raman shifts are well summarized by Adachi.…”

Section: Gaas-like Optical Modesmentioning

confidence: 99%

Raman scattering studies of strain effects in (100) and (311)B GaAs1−xBix epitaxial layers

Steele

Lewis

Henini

et al. 2013

We report room-temperature Raman studies of strained (100) and (311)B GaAs1-xBix epitaxial layers for x ≤ 0.039. The Raman spectra exhibit a two-mode behavior, as well as disorder-activated GaAs-like phonons. The experimental results show that the GaAs-like LO(Γ) mode experiences a strong composition-dependent redshift as a result of alloying. The peak frequency decreases linearly from the value for pure GaAs (∼293 cm-1) with the alloyed Bi fraction x and the introduced in-plane lattice strain ε, by Δ ω LO = Δ ω alloy-Δ ω strain. X-ray diffraction measurements are used to determine x and ε allowing Δ ω alloy to be decoupled and is estimated to be-12(±4) cm-1/x for (100) GaAs1-xBix. Δ ω LO is measured to be roughly double for samples grown on (311)B-oriented substrates to that of (100) GaAs. This large difference in redshift is accounted for by examining the Bi induced strain, effects from alloying, and defects formed during high-index (311)B crystal growth. Raman scattering studies of strain effects in (100) and (311) We report room-temperature Raman studies of strained (100) and (311)B GaAs 1Àx Bi x epitaxial layers for x 0.039. The Raman spectra exhibit a two-mode behavior, as well as disorder-activated GaAs-like phonons. The experimental results show that the GaAs-like LO(C) mode experiences a strong composition-dependent redshift as a result of alloying. The peak frequency decreases linearly from the value for pure GaAs ($293 cm À1) with the alloyed Bi fraction x and the introduced in-plane lattice strain e k , by Dx LO ¼ Dx alloy À Dx strain . X-ray diffraction measurements are used to determine x and e k allowing Dx alloy to be decoupled and is estimated to be À12(64) cm À1

“…This peak is observed due to a disorder-induced relaxation of the selection rules, as occurs for instance in dilute GaAsN. 20 In the particular case of the spectrum displayed in Fig. 3, both the InAs-like TO and LO modes are slightly shifted to lower frequencies with respect to bulk InAs ͑we measure TO and LO frequencies at 80 K for bulk InAs grown on GaAs at 220 cm −1 and 242 cm −1 , respectively; Carles et al 21 report similar values͒.…”

Section: Vibrational Spectroscopiesmentioning

confidence: 87%

“…22 and 20͒ and in the GaAs-and InAs-like LO modes of InGaAsN, 23 reflect the strain state of the epilayers as well as the effect of alloying on the phonon frequencies. 20 A clear feature is observed between the InAs-like TO and LO peaks. A similar Raman band has been previously observed in n-type InAs samples and attributed to an LOplasmon coupled mode ͑LOPCM͒.…”

Section: Vibrational Spectroscopiesmentioning

confidence: 93%

Structural and optical properties of dilute InAsN grown by molecular beam epitaxy

Ibáñez

Oliva

Mare

et al. 2010

Self Cite

We perform a structural and optical characterization of InAs 1−x N x epilayers grown by molecular beam epitaxy on InAs substrates ͑x Շ 2.2%͒. High-resolution x-ray diffraction ͑HRXRD͒ is used to obtain information about the crystal quality and the strain state of the samples and to determine the N content of the films. The composition of two of the samples investigated is also obtained with time-of-flight secondary ion mass spectroscopy ͑ToF-SIMS͒ measurements. The combined analysis of the HRXRD and ToF-SIMS data suggests that the lattice parameter of InAsN might significantly deviate from Vegard's law. Raman scattering and far-infrared reflectivity measurements have been carried out to investigate the incorporation of N into the InAsN alloy. N-related local vibrational modes are detected in the samples with higher N content. The origin of the observed features is discussed. We study the compositional dependence of the room-temperature band gap energy of the InAsN alloy. For this purpose, photoluminescence and optical absorption measurements are presented. The results are analyzed in terms of the band-anticrossing ͑BAC͒ model. We find that the room-temperature coupling parameter for InAsN within the BAC model is C NM = 2.0Ϯ 0.1 eV.