Dielectric response of wurtzite gallium nitride in the terahertz frequency range

Hibberd, M. T.; Frey, V.; Spencer, Ben F.; Mitchell, P.W.; Dawson, Philip E.; Kappers, M. J.; Oliver, Rachel A.; Humphreys, C. J.; Graham, D. M.

doi:10.1016/j.ssc.2016.08.017

Cited by 27 publications

(9 citation statements)

References 23 publications

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“…The calculated unstrained in-plane (ε ⊥ ∞ ) and out-of-plane (ε ∞ ) high-frequency dielectric constants are 5.60 and 5.77, respectively. These values slightly overestimate the experimental values of ε ⊥ ∞ =5.14 120 , 5.25 121 , 5.29 122 or 5.35 123 as well as ε ∞ =5.31 120 , 5.41 121 . The corresponding in-plane and out-of-plane Born effective charges are 2.59 and 2.73, respectively; these values are in agreement with earlier theoretical values of 2.60 and 2.74, respectively 110 .…”

Section: B Phonon Dispersion Relationscontrasting

confidence: 54%

Hole mobility of strained GaN from first principles

2019

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Nitride semiconductors are ubiquitous in optoelectronic devices such as LEDs and Blu-Ray optical disks. A major limitation for further adoption of GaN in power electronics is its low hole mobility. In order to address this challenge, here we investigate the phonon-limited mobility of wurtzite GaN using the ab initio Boltzmann transport formalism, including all electron-phonon scattering processes, spin-orbit coupling, and many-body quasiparticle band structures. We demonstrate that the mobility is dominated by acoustic deformation-potential scattering, and we predict that the hole mobility can significantly be increased by lifting the split-off hole states above the light and heavy holes. This can be achieved by reversing the sign of the crystal-field splitting via strain or via coherent excitation the A1 optical phonon through ultrafast infrared optical pulses. arXiv:1908.02072v1 [cond-mat.mtrl-sci]

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Section: B Phonon Dispersion Relationscontrasting

confidence: 54%

Hole mobility of strained GaN from first principles

2019

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“…By introducing the screening effect into the GaN-based system, we set the parameters m* = 0.2m (considering the light hole of GaN in reference 40 ), where m is electron rest mass, ε ∞ = 5.35 (in reference 41 ), N = 5 × 10 16 cm −3 , which is a typical hole density in p-doped GaN-based blue LED 42 . The initial refractive index n 0 ∼3 was referred to the experimental results in reference 43 such that the initial transmitted THz waveform is E(t) = 2E inc (t)/(1 + n 0 ), where E inc (t) is the incident THz pulse, and E(t) is the transmitted THz pulse at the interface between GaN and air. Furthermore, as to obtain the full frequency-dependent refractive index, we implemented the Fast Fourier Transform (FFT) against the THz temporal profile and calculated frequency-dependent refractive index every time when the carrier density changed.…”

Section: Methodsmentioning

confidence: 99%

Terahertz strong-field physics in light-emitting diodes for terahertz detection and imaging

Ouyang

et al. 2021

Commun Phys

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Intense terahertz (THz) electromagnetic fields have been utilized to reveal a variety of extremely nonlinear optical effects in many materials through nonperturbative driving of elementary and collective excitations. However, such nonlinear photoresponses have not yet been obeserved in light-emitting diodes (LEDs), let alone employing them as fast, cost-effective, compact, and room-temperature-operating THz detectors and cameras. Here, we report ubiquitously available LEDs exhibiting photovoltaic signals of ~0.8 V and ~2 ns response time with signal-to-noise ratios of ~1300 when being illuminated by THz field strengths ~240 kV/cm. We also demonstrated THz-LED detectors and camera prototypes. These unorthodox THz detectors exhibited high responsivities (>1 kV/W) with response time four orders of magnitude shorter than those of pyroelectric detectors. The mechanism was attributed to THz-field-induced impact ionization and Schottky contact. These findings not only help deepen our understanding of strong THz field-matter interactions but also contribute to the applications of strong-field THz diagnosis.

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“…at 568.6 cm −1 is slightly shifted from bulk GaN, (GaN bulk ) at 567.4 cm −1 [8], whereas the (AlN substr. ) at 658 cm −1 is nearly identical with that of bulk AlN, (AlN bulk ) at 656.7 ± 2.4 cm −1 [45][46][47][48][49][50][51][52]. The shift to the higher frequency in both cases indicates compressive residual stress in the template layers [33].…”

Section: Resultsmentioning

confidence: 78%

Coherent-interface-induced strain in large lattice-mismatched materials: A new approach for modeling Raman shift

et al. 2021

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Strain engineering as one of the most powerful techniques for tuning optical and electronic properties of Ill-nitrides requires reliable methods for strain investigation. In this work, we reveal, that the linear model based on the experimental data limited to within a small range of biaxial strains (< 0.2%), which is widely used for the non-destructive Raman study of strain with nanometer-scale spatial resolution is not valid for the binary wurtzite-structure group-III nitrides GaN and AlN. Importantly, we found that the discrepancy between the experimental values of strain and those calculated via Raman spectroscopy increases as the strain in both GaN and AlN increases. Herein, a new model has been developed to describe the strain-induced Raman frequency shift in GaN and AlN for a wide range of biaxial strains (up to 2.5%). Finally, we proposed a new approach to correlate the Raman frequency shift and strain, which is based on the lattice coherency in the epitaxial layers of superlattice structures and can be used for a wide range of materials. Electronic Supplementary Material Supplementary material is available for this article at 10.1007/s12274-021-3855-4 and is accessible for authorized users.

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Dielectric response of wurtzite gallium nitride in the terahertz frequency range

Cited by 27 publications

References 23 publications

Hole mobility of strained GaN from first principles

Hole mobility of strained GaN from first principles

Terahertz strong-field physics in light-emitting diodes for terahertz detection and imaging

Coherent-interface-induced strain in large lattice-mismatched materials: A new approach for modeling Raman shift

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