Polar Optical Phonon Instability and Intervalley Transfer in Gallium Nitride

1998 ◽  
Vol 512 ◽  
Author(s):  
B. E. Foutz ◽  
S. K. O'leary ◽  
M. S. Shur ◽  
L. F. Eastman ◽  
B. L. Gelmont ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
Analytical Model ◽  
Optical Phonon ◽  
Room Temperature ◽  
Phonon Scattering ◽  
Polar Optical Phonon ◽  
Scattering Mechanism ◽  
Loss Mechanism ◽  
One Dimensional ◽  
Optical Phonon Scattering

ABSTRACTWe develop a simple, one-dimensional, analytical model, which describes electron transport in gallium nitride. We focus on the polar optical phonon scattering mechanism, as this is the dominant energy loss mechanism at room temperature. Equating the power gained from the field with that lost through scattering, we demonstrate that beyond a critical electric field, 114 kV/cm at T = 300 K, the power gained from the field exceeds that lost due to polar optical phonon scattering. This polar optical phonon instability leads to a dramatic increase in the electron energy, this being responsible for the onset of intervalley transitions. The predictions of our analytical model are compared with those of Monte Carlo simulations, and are found to be in satisfactory agreement.

scholarly journals Prediction of higher thermoelectric performance in BiOCuSe by weakening electron-polar optical phonon scattering

2020 ◽  
Author(s):  
Tianqi Zhao ◽  
Quinn Gibson ◽  
Luke Daniels ◽  
Ben Slater ◽  
Furio Cora
Keyword(s):  
Carrier Mobility ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Phonon Scattering ◽  
Hole Mobility ◽  
Polar Optical Phonon ◽  
First Principles Calculations ◽  
Thermoelectric Figure ◽  
Optical Phonon Scattering ◽  
Electron Phonon Scattering

Abstract BiOCuSe is a promising thermoelectric material, but its applications are hindered by low carrier mobility. We use first principles calculations to analyse electron-phonon scattering mechanisms and evaluate their contributions to the thermoelectric figure of merit ZT. The combined scattering of carriers by polar optical (PO) and longitudinal acoustic (LA) phonons yields an intrinsic hole mobility of 32 cm2 V-1 s-1 at room temperature and a temperature power law of T-1.5, which agree well with experiments. We demonstrate that electron phonon scattering in the Cu-Se layer dominates at low T, while contributions from the Bi-O layer become increasingly significant at higher T. At room temperature, ZT is calculated to be 0.48 and can be improved by 30% through weakening PO phonon scattering in the Cu-Se layer. This finding agrees with the experimental observation that weakening the carrier-phonon interaction by Te substitution in the Cu-Se layer improves mobility and ZT. At high T, the figure of merit is improved by weakening phonon scattering in the Bi-O layer instead. The theoretical ZT limit of BiOCuSe is calculated to be 2.5 at 875 K.

scholarly journals Crystallographic Orientation Effect On Hole Polar Optical Phonon Scattering Rates in Thin Gaas/Alxga1-Xas Quantum Wells

2019 ◽  
Author(s):  
Mohamed Boumaza
Keyword(s):  
Quantum Wells ◽  
Optical Phonon ◽  
Phonon Scattering ◽  
Strain Effect ◽  
Polar Optical Phonon ◽  
Phonon Modes ◽  
Bulk Gaas ◽  
Hole Energy ◽  
Optical Phonon Scattering ◽  
Scattering Rates

We report on hole polar optical phonon scattering processes in thin GaAs/AlxGa1-xAs quantum wells grown in various crystallographic directions, such as [001], [110]. Using the dielectric continuum model we focus on how the different scattering processes of holes with interface phonon modes depend on the initial hole energy. In our work, we use the Luttinger-Kohn (LK) 6×6 k.p Hamiltonian with the envelope function approximation, from which we compute numerically the electronic structure of holes for a thin quantum well sustaining only one bound state for each type of hole. Due to mixing between the heavy, light, and split off bands, hole subbands exhibit strong nonparabolicity and important warping that have their word to say on physical properties. Detailed and extensive calculations that the rates for intra-subband scattering processes differ significantly from those of bulk GaAs because of quantization and reduced dimensionality. Moreover, the study of scattering as a function of hole energy shows that the trend of the scattering rates is governed mostly by i) overlap integrals and ii) the density of the final states to which the hole scatters. The influence of warping, in the hole energy dispersion, on the phonon scattering rates is also explored and found to be important when the initial hole energy is high. Our calculations show evidence of strong anisotropy in the scattering rates especially for processes involving the heavy hole subband, which anisotropy is in fact quite important and far from being negligible. However, strain effect can reduce scattering rates.

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