Magnetopolaron effect on shallow donors in GaN

Abstract

Resonant interaction between longitudinal-optic ͑LO͒ phonons and electrons bound on shallow donors in GaN is studied using magnetoluminescence of neutral-donor bound excitons ͑D 0 X͒. The experiments were performed on high-quality freestanding GaN material and heteroepitaxial GaN layers grown on sapphire. In addition to the principal recombination channel of D 0 X, in which donors are left in their ground states, two-electron satellites ͑TES͒ involving different excited donor excitations, as well as replicas of the principal D 0 X transition due to LO phonons, were observed for the oxygen and silicon donors. In order to separate transitions involving ground and excited D 0 X states, variable-temperature experiments were performed. The application of high magnetic fields allows tuning of the donor excitations into resonance with the LO phonon energy. This results in a strong enhancement of TES intensity and the appearance of several anticrossing processes in the vicinity of a LO phonon replica of the principal D 0 X transition. The observed behavior is explained in terms of a resonant interaction between LO phonons and donor-bound electrons ͑magnetopolaron effect͒. The experimental data are described using a phenomenological model that combines the theory of a hydrogen atom in a magnetic field with a model which includes the effects of nonparabolicity, nonresonant polaron corrections, and the resonant magnetopolaron effect on electrons bound to donors. It was found that the interaction in the resonant magnetopolaron regime is stronger for the oxygen than for the silicon donor.

Transient photoluminescence of shallow donor bound excitons in GaN

“…10,11 Excited states of the neutral donors have recently been studied in TET spectra by several authors, with some discrepancy in the interpretations. 8,[12][13][14][15] Our recent studies of high resolution TET spectra for O and Si donors in GaN ͑Ref. 16͒ give results for the energies of the excited donor states very similar to Ref.…”

Theory of Bernstein modes in graphene

“…Experimentally, Bernstein modes have been observed in 2D electron systems in semiconductor heterostructures. [12][13][14][15][16] In contrast to three-dimensional metals, 23 the main difficulty stems from the vanishing plasmon dispersion at q = 0, such that a direct measurement of Bernstein modes in homogeneous 2D systems via spectroscopic means is impossible. It is therefore necessary to impose a non-zero value of the wave vector to the system.…”

Influence of Landau levels on the phonon dispersion of Weyl semimetals

“…At resonance, the phonon and the plasmon couple strongly and an avoided crossing (or "anticrossing") emerges between the two dispersion branches. Even though there exists an extensive literature on the plasmon-phonon hybridization in polar semiconductors, both in the absence and in the presence of magnetic fields, 28,[33][34][35] in WSM the hybridization at long wavelengths is induced by magnetic fields even when the material is intrinsically nonpolar. As we elaborate below, the hybridization gap in this case is about an order of magnitude smaller than in polar semiconductors like GaAs, though it may reach observability at high magnetic fields.…”