Ionization Degree of Electron-Hole Plasma in GaN/AlGaN Quantum Wells

Nikolaev, V. V.; Portnoi, M. E.

doi:10.1002/1521-396x(200203)190:1<113::aid-pssa113>3.0.co;2-h

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phys. stat. sol. (a)

2002

DOI: 10.1002/1521-396x(200203)190:1<113::aid-pssa113>3.0.co;2-h

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Ionization Degree of Electron-Hole Plasma in GaN/AlGaN Quantum Wells

V. V. Nikolaev

M. E. Portnoi

Abstract: We study statistical properties of a strongly separated electron-hole plasma in an undoped GaN/ AlGaN quantum well. We use a self-consistent approach, which is based on the proper account of the impact of screening on bound and scattered states. A new mechanism of screening of Coulomb interaction by spatially indirect excitons is proposed and investigated within the framework of the Thomas-Fermi approximation. We calculate the ionization degree as a function of total carrier density for different quantum well … Show more

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Cited by 3 publications

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Theory of excitonic Mott transition in double quantum wells

Nikolaev

Portnoi

2004

phys. stat. sol. (c)

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We consider an electron-hole system in double quantum wells theoretically. We demonstrate that there is a temperature interval over which an abrupt jump in the value of the ionization degree occurs with an increase of the carrier density or temperature. The opposite effect -the collapse of the ionized electron-hole plasma into an insulating exciton system -should occur at lower densities. In addition, we predict that under certain conditions there will be a sharp decrease of the ionization degree with increasing temperature -the anomalous Mott transition. We discuss how these effects could be observed experimentally.PACS numbers: 71.35.Ee, 73.21.Fg It was suggested by Mott [1] that an increase of the temperature or density of an insulating system of excitons may lead to avalanche ionization as a result of screening and k-space filling. Despite significant efforts [2,3,4,5,6], there is still no firm theoretical understanding of this effect, and the existence of the transition is disputed.In bulk indirect-bandgap semiconductors, experimental observation of the Mott transition is prevented by the formation of electron-hole liquid (EHL) droplets [7]. The absence of low-temperature phase transitions in direct semiconductors and single quantum wells is believed to be caused by fast radiative recombination, which does not allow enough time for the photo-generated electron-hole plasma (EHP) to cool down.In recent years there has been increased attention towards double quantum wells (DQWs) -heterostructures containing two quantum wells (QWs) situated close enough so that the Coulomb correlations between particles in different QWs are significant. Electrons and holes from adjacent QWs form spatially indirect excitons (IXs) with very long lifetimes, due to the small electron-hole (e-h) wavefunction overlap. The experimentally confirmed long life-time and stability of the DQW indirect exciton [8,9,10,11,12] suggests that the formation of a medium-density cold exciton gas is possible. Under certain conditions this gas may undergo a Mott transition.Another property beneficial for observation of the Mott transition in a DQW is that the spatially separated EHP posses substantial electrostatic energy (Hartree term in the self-energy). This leads to the fact that for large enough separation of quantum wells there is no minimum in the dependence of the ground-state energy on the density, and thus the formation of e-h droplets is not possible [5,13].The purpose of this Letter is to investigate the possibility of a Mott transition in DQW systems and to encourage further experimental research.The main theoretical difficulty in investigation of the Mott transition is that it is inherently a medium-density effect, for which low-density and high-density approximations do not work. The correct approach would require careful handling of the Coulomb interaction depending on the thermodynamic state of the system, which implies a self-consistent procedure.Before studying the Mott transition, which is essentially a jump in the ionization...

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Theory of excitonic Mott transition in double quantum wells

Nikolaev

Portnoi

2004

phys. stat. sol. (c)

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Theory of the excitonic Mott transition in quasi-two-dimensional systems

Nikolaev

Portnoi

2008

Superlattices and Microstructures

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Coulombic effects of electron-hole plasma in nitride-based nanostructures

Fedorov

Sokolov

Zavada

2005

Journal of Applied Physics

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We study the Coulombic effects of electron-hole plasma on the ground and first excited energy levels and carrier wave functions in a GaN∕AlGaN quantum well (QW) structure. The coupled Schrödinger equations for electron and hole states are solved self-consistently in the Hartree-Fock approximation along with the Poisson equation. As expected, the decreasing QW width and increasing plasma density diminish the charge separation in the QW induced by the internal field, leading to the relatively reduced contribution of the Hartree interaction to the energy-level shift. In contrast, the calculation also demonstrates that the contribution of many-body effects becomes more pronounced. The resulting competition between the many-body and Hartree contributions causes a nonmonotonous dependence of the electron and hole energies on the plasma density at a given field. These findings are applied to explore the potential bistable behavior in the QW electroabsorption under near-band-edge photoexcitation.

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Ionization Degree of Electron-Hole Plasma in GaN/AlGaN Quantum Wells

Cited by 3 publications

References 12 publications

Theory of excitonic Mott transition in double quantum wells

Theory of excitonic Mott transition in double quantum wells

Theory of the excitonic Mott transition in quasi-two-dimensional systems

Coulombic effects of electron-hole plasma in nitride-based nanostructures

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