List of Abstracts from Group Publications

Boltzmann kinetic equation with correction term for intracollisional field effect

K. Kalna

Abstract:

We have included a higher order term in the approximation of electron density matrix on the way to the derivation of the Boltzmann kinetic equation from the Liouville-von Neumann equation by means of Kubo's formalism. This higher term has been added to the Boltzmann kinetic equation as the correction term. In a simplified case the field effect collision rate is introduced representing intracollisional field effect. The correction term gives a significant contribution to the Boltzmann kinetic equation for the electric field strength of 2.5 MV/m which was determined by the numerical calculation.

Source:

Semicond. Sci. Technol. 7 (1992) 1446-1452.

Electron-electron scattering induced capture in GaAs quantum wells

K. Kalna, M. Mosko, and F. M. Peeters

Abstract:

Electron capture times in a separate confinement quantum well (QW) with finite electron density are calculated for electron-electron (e-e) and electron-polar optic phonon (e-pop) scattering. In both cases the capture time versus QW width oscillates with the same period, but with the quite different amplitude. For electron density of 10¹¹ cm^-2 the e-e capture time is 10¹-10³ times larger than the e-pop capture time except for QW widths near resonance minima. Near the resonances it is only 2-3 times larger and at high enough electron densities even smaller than the e-pop capture time. Thus the capture efficiency of a quantum well with optimized (resonant) well width can be further optimized by varying the carrier density.

Source:

Lithuanian J. Phys. 35 (1995) 435-439.

Electron capture in GaAs quantum wells via electron-electron and optic phonon scattering

K. Kalna, M. Mosko, and F. M. Peeters

Abstract:

Electron capture times in a quantum well (QW) structure with finite electron density are calculated for electron-electron (e-e) and electron-polar optic phonon (e-pop) scattering. We find that the capture time oscillates as function of the QW width for both processes with the same period, but with very different amplitudes. For an electron density of 10¹¹ cm^-2 the e-e capture time is 10¹-10³ times larger than the e-pop capture time except for QW widths near the resonance minima, where it is only 2-3 times larger. With increasing density the e-e capture time decreases and near the resonance becomes smaller than the e-pop capture time. Our e-e capture times are three orders larger than results of Blom et al. [Appl. Phys. Lett. 62, 1490 (1993)]. The role of the e-e capture in QW lasers is readdressed.

Source:

Appl. Phys. Lett. 68 (1996) 117-119.

Carrier capture due to carrier-carrier interaction in quantum wells

K. Kalna and M. Mosko

Abstract:

Electron capture times in a separate confinement quantum well (QW) with finite electron density are calculated for electron-electron (e-e) and electron-polar optic phonon (e-pop) scattering. In both cases the capture time versus QW width oscillates with the same period, but with the quite different amplitude. For electron density of 10¹¹ cm^-2 the e-e capture time is 10¹-10³ times larger than the e-pop capture time except for QW widths near resonance minima. Near the resonances it is only 2-3 times larger and at high enough electron densities even smaller. Thus the resonant capture can be optimized by varying the carrier density.

Source:

in: Heterostructure Epitaxy and Devices, Ed. by J. Novak and A. Schlachetzki, NATO ASI Series, Kluwer Academic Publishers, Dordrecht (1996) 79-82.

Electron capture into quantum wells via scattering by electrons, holes, and optical phonons

K. Kalna and M. Mosko

Abstract:

Electron capture times due to the electron-electron (e-e), electron-hole (e-h) and electron-polar optical phonon (e-pop) interactions are calculated in the GaAs quantum well (QW) with electron and hole densities 10¹¹ cm^-2. The calculated capture times oscillate as a function of the QW width with the same period but with different amplitudes. The e-h capture time is two to four orders larger and the e-e capture time one to three orders larger than the e-pop capture time. The exceptions are the QW widths near resonance minima, where the e-e capture time is only 2-3 times larger and the e-h capture time 10-100 times larger. Different physical origin of the oscillatory behavior is demonstrated for the e-e and e-pop capture times. Effects of exchange and degeneracy on the e-e capture are analysed. The exchange effect increases the e-e capture time approximately two times while the degeneracy does not change the capture time except for the QW depths and widths near the resonance.

Source:

Phys. Rev. B 54 (1996) 17730-17737.

Phonon confinement and electron capture time in quantum well

K. Kalna

Abstract:

The electron capture time via an electron-polar optical phonon interaction is calculated considering the confinement of a phonon in a GaAs quantum well (QW) laser structure. The effect of the phonon confinement decreases the electron capture time about two times comparing to the electron capture time obtained from the interaction of an electron with the bulk phonon.

Source:

Acta Phys. Pol. A 92 (1997) 805-808

Carrier capture into a GaAs quantum well with a separate confinement region: Comment on quantum and classical aspects

M. Mosko and K. Kalna

Abstract:

We study the optic-phonon-mediated carrier capture in a narrow GaAs quantum well with a 100-nm separate confinement region. In a standard quantum model the capture means the carrier scattering from the energy subband above the quantum well into a subband in the quantum well. We use the quantum model in parallel with a classical model in which a classical carrier is captured during collisionless motion when emitting the optic phonon inside the GaAs layer. Comparison with the experiment of Blom et al. [Phys. Rev. B 47, 2072, (1993)] suggests that the quantum capture model is valid not only for electrons but also for heavy holes in case of very narrow (2.6-nm) quantum wells. In case of wider quantum wells the available experimental data support equally the quantum as well as classical hole capture models and do not allow to draw a definite conclusion. Finally, the effect of the phonon confinement on the quantum capture is evaluated and discussed.

Source:

Semicond. Sci. Technol. 14 (1999) 790-796.