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3 Acta Physica Polonica A

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Long Decays of Excitonic Photoluminescence from CdTe/ZnTe Individual Quantum Dots

100%

Piechal B. , Suffczyński J. , Trajnerowicz A. , Goryca M. , Kossacki P. , Golnik A. , Gaj J.

Acta Physica Polonica A

2005

tom 108

nr 5

831-836

We present time-resolved micro-photoluminescence study of self-assembled CdTe/ZnTe quantum dots. In addition to the fast radiative decay of the exciton, we observe long components, being of the order of a few nanoseconds. We observe that long decays are present for neutral exciton lines as well as on the biexciton ones. The temperature dependent measurements reveal the non-monotonic behaviour. We find also that the long decays are not mono-exponential. We conclude that the dark exciton states cannot be treated as the only source of long decays in the luminescence. We propose other possible explanation, which is the slowing of luminescence by carrier trapping in high energy states in quantum dots and barriers.

Pressure and Temperature Dependence of Threshold Current in Semiconductor Lasers Based on InGaAs/GaAs Quantum-Well Systems

100%

Maziarz M. , Piechal B. , Bercha A. , Bohdan R. , Trzeciakowski W. , Majewski J.

Acta Physica Polonica A

2007

tom 112

nr 2

437-442

In the present paper we demonstrate that wide-range wavelength tuning of semiconductor lasers can be achieved by applying high pressure and low temperature. We report the experimentally measured dependence of the threshold current and emission energy on pressure and temperature in InGaAs/GaAs quantum-well lasers and provide the simple theoretical explanation of the physics behind the experimental findings.

Many-Body Interactions in the CdTe-Based Quantum Well under Strong Optical Excitation

84%

Płochocka P. , Kossacki P. , Piechal B. , Maślana W. , Golnik A. , Cibert J. , Tatarenko S. , Gaj J.

Acta Physica Polonica A

2004

tom 106

nr 3

413-422

We performed pump-probe time-resolved absorption measurements on a modulation p-doped (Cd,Mn)Te quantum well. The density of the 2D hole gas was controlled, in the 10^{10} cm^{-2} range, by additional cw illumination. Interactions between photocreated neutral (X) and charged (X^{+}) excitons and the 2D hole gas were analyzed. We found that the strongest effect is the influence of the carriers on both X and X^+ optical resonances. Neutral and charged excitons are screened by holes, which results in the decrease in their intensities. We conclude from polarization resolved experiments that this screening is spin-dependent: it is more efficient between holes with opposite spins. Binding holes into the charged excitons reduces the screening of the neutral excitons and leads to an enhancement of the neutral exciton intensity. We also analyzed weaker effects, due to exciton-exciton interaction, at a constant hole density. We found that the reduction of the neutral exciton intensity due to two different mechanisms (phase-space filling and biexciton formation) is almost equal. We observed a spin-dependent blue shift of the neutral exciton line in the presence of a population of neutral excitons created by the pump pulse. Due to the attractive interaction between excitons with opposite spins, the corresponding shift of the neutral exciton is smaller than that observed due to the interaction between excitons with the same spins.