Applicability of the Fermi golden rule and the possibility of low-field runaway transport in nitrides

Abstract

In order to justify applicability of the standard approach of perturbation theory for the description of transport phenomena in wide-band polar semiconductors with strong electron-phonon interactions, we have compared dependences of energy losses to the lattice on the electron drift velocity obtained for different materials in the frameworks of (a) a perturbative approach based on calculation of the scattering rates from Fermi's golden rule and (b) a non-perturbative approach based on the path-integral formalism of Thornber and Feynman. Our results reveal that despite strong electronphonon coupling in GaN and AlN such that intercollision times become of the order of the period of phonon oscillation, standard perturbative treatment can still be applied successfully for this type of material. Our findings also indicate possibility for unique long-distance runaway transport in nitrides which may occur at the pre-threshold electric fields. Polaron ground state energy and effective masses are calculated for GaN and AlN as well as for GaAs and Al2O3.

Electron–phonon interaction in zinc oxide. Plasmon–optical phonon coupled modes

“…Since plasma oscillations mix the symmetry properties of E 1 and A 1 modes and their LO/TO character, resulting in both Raman and IR active vibrations as experimentally evidenced [18,24]. With these in mind we are right in believ- ing that the third branch, 3 ω may also be both a Raman and IR active vibration. All these modes are plotted in Fig.…”

“…The other three are the plasmon-optical phonon coupled modes dispersion laws. Additionally to 1 ω and 2 ω modes (often noted , ω ω + -in the literature) [17][18][19]22], due to uniaxial anisotropy of the system, a third branch, 3 ω appears. It lies in the ( ||,TO ,TO , ω ω^) frequency domain.…”

“…The particles would have a random orientation of the optical axis with respect the normal at the surface, covering continuously the interval (0, π/2). This should be reflected in a broad vibrational band downshifted with respect A 1 (TO) frequency for 1 { } ω modes, an up-shifted one with respect E 1 (LO) for 2 { } ω and another, corresponding to 3 { } ω modes, in 380-415 cm -1 frequency range, depending on free electron density and orientation with respect the surface. …”

“…In the past years, much effort has been devoted in investigating their physical properties. Understanding their lattice dynamics behaviour is of great interest too [1][2][3].…”

Scattering of electrons by polar optical phonons in AlGaN/GaN single heterostructures

“…In the case of intermediate electron-phonon interaction strength some care is needed. In the case of wurtzite GaN and AlN it was found that the usual perturbative treatment (FermiÕs Golden Rule) can be applied [34] in spite of the relatively strong electron-phonon coupling in these materials. This conclusion was reached by comparing the results obtained in the framework of a perturbative approach based on the calculation of scattering rates by the FermiÕs Golden Rule and those obtained with a nonperturbative approach based on the path-integral formalism of Thornber and Feynman [35].…”