Carrier-induced changes of the phase of reflected light at a pumped ZnSe layer

Henneberger

2009

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As a first detailed study on the basis of a recently found basic law for the non‐equilibrium energy flow in bounded media, we examine the absorption spectra of an excited semiconductor slab and present detailed calculations for its emission spectra in quasi‐equilibrium. The density of excited carriers is varied from the excitonic regime up to densities where gain appears.Different slab lengths are regarded, and the dependence on the angle of incidence is studied. The absorption and emission spectra follow the Fabry‐Perot resonances in the slab. Depending on its length, excitation, and the position of the resonances, the formation of sharp and strong emission lines is observed, and degeneracy effects become apparent. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Section: Susceptibilitymentioning

confidence: 99%

Quasi‐equilibrium emission of excited semiconductors

Richter

Henneberger

2009

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“…In [1] the basic theoretical concept was presented to include the dynamic screening between excited carriers. This concept has been extended to the dielectric response in semiconductors in order to describe the phase and amplitude of light propagating through semiconductor heterostructures [2,3] for excitations well below the Mott transition of excitons. In recent experiments [4,5] the resonant Rayleigh scattering from localized electron-hole (eh) pair states in GaAs-AlGaAs quantum wells has been investigated, showing at high excitation the transition from excitonic to plasma emission over a wide range of the density of excited carriers and temperatures.…”

Section: Introductionmentioning

confidence: 99%

Transition from excitonic to plasma emission from localized electron‐hole pair states in GaAs‐AlGaAs quantum wells

Richter

Semkat

et al. 2011

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We present a theoretical analysis of the emission of localized excitons in GaAs‐AlGaAs quantum wells, which shows a strong nonlinear behavior with increasing excitation. Considering the influence of dynamical screening both on the one‐particle properties of carriers and on the whole spectrum of electron‐hole pair states, we are able to explain the nonlinearity as a transition of the emission from excitonic to electron‐hole pair states in the continuum (electron‐hole plasma). Moreover, our theoretical approach based on the quasi‐particle approximation for the carriers states and quantum kinetic effects in the screening describes the observed changes of the shift of the exciton energy from higher to lower energies at a temperature of T = 10 K (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

“…This could be explained by a carrier-induced asymmetry of the exciton line. Carrierinduced changes of the spectral phase of the complex coefficient of reflection were investigated in [10,11]. In [11] it was found for a ZnSe sample, that the phase exhibits a global change at the hh-exciton by 2π.…”

Section: Introductionmentioning

confidence: 99%

“…Carrierinduced changes of the spectral phase of the complex coefficient of reflection were investigated in [10,11]. In [11] it was found for a ZnSe sample, that the phase exhibits a global change at the hh-exciton by 2π. Injecting additional carriers by a weak pump pulse the step-like jump changes its direction to −π, which could be attributed to a small carrier-induced increase of the exciton linewidth.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mott transition of excitons in ZnSe studied by phase resolved reflection

Henneberger

Seemann

et al. 2009

The Mott transition of excitons in a semiconductor with increasing carrier density is in principle well understood as a consequence of screening of the Coulomb interaction between carriers. While the position of the exciton stays widely unchanged the exciton peak disappears due to band gap shrinkage. However, a more quantitative check of applied theoretical models for the screening and of the role of quantum kinetic effects in this process is still open.We demonstrate that the phase‐resolved reflection in shallow‐confined ZnSSe heterostructures opens the possibility of a detailed study of the Mott transition due to the appearance of pronounced interferences effects of propagating polariton modes.Our theoretical approach for the investigation of the influence of excited carriers on the dielectric susceptibility is based (i) on a quasi‐particle approximation for the carrier energies and damping, and (ii) on the semiconductor Bloch equations including dynamical screening and a quantum kinetic treatment of scattering. These manybody effects lead to drastic changes of both amplitude and phase of the reflected light: Jumps of the phase are steepened, show abrupt changes from +π to –π and are smoothed out, and interference peaks in the amplitude decrease and disappear completely with increasing excitation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)