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Influence of Built-in Electric Field on Forbidden Transitions in In_xGa_{1-x}As/GaAs Double Quantum Well by Three-Beam Photoreflectance

100%

Sęk G., Ryczko K., Misiewicz J., Bayer M., Wang T., Forchel A.

Acta Physica Polonica A

2001

vol. 100

issue 3

417-424

Photoreflectance spectroscopy has been used to study optical transitions in In_{0.045}Ga_{0.955}As/GaAs double quantum well at 80 K. The derivative nature of this contactless electromodulation technique allows for the observation of excited state transitions in the low-dimensional structure including the symmetry-forbidden ones. Excitonic symmetry-forbidden transitions can be observed due to the effect of mixing of heavy and light hole excitons and/or due to some asymmetry in the structure. We have shown that the built-in electric field in the region of double quantum well is weak enough (less than 0.5 kV/cm) not to cause any significant energetic shift of features due to quantum confined Stark effect, on one hand. On the other hand, it is sufficient to change strongly the oscillator strength of forbidden transitions. To change the internal electric field, we have used photoreflectance in the three-beam mode with a third beam continuously illuminating the sample and causing changes of the built-in electric fields due to the photovoltage effect. This method works as a contactless forward bias and allows for a change of the field down to the flat band conditions. We have shown that changes of built-in electric field by amount of a few tenths of kV/cm can modify the intensity of forbidden transitions significantly. We show that, although the mixing of excitons is still important, a very weak built-in electric field can be dominant in the observation of forbidden excitonic transitions in double quantum well.

Exciton Exchange between Nearly-Free and Acceptor-Bound States of a Positive Trion Assisted by Cyclotron Excitation

84%

Jadczak J., Bryja L., Wójs A., Bartsch G., Yakovlev D., Bayer M., Plochocka P., Potemski M., Reuter D., Wieck A.

Acta Physica Polonica A

2011

vol. 119

issue 5

600-601

In magneto-photoluminescence spectra of a two-dimensional hole gas in a GaAs quantum well we observe coupling of two different radiative states. The pair of coupled states are an acceptor-bound trion AX^{+} and an essentially free (only weakly localized by a shallow lateral potential) trion X^{+}, brought into resonance by an additional cyclotron excitation controlled by the magnetic field. The coupling mechanism is the exciton transfer, and the optical signature is a clear anticrossing of the emission lines of an X^{+} and a cyclotron replica of the AX^{+}.

Electron Spins in Self-Assembled (In,Ga)As/GaAs Quantum Dots Studied by Pump-Probe Faraday Rotation

68%

Greilich A., Yugova I., Oulton R., Zhukov E., Yakovlev D., Bayer M., Shabaev A., Efros A., Stavarache V., Reuter D., Wieck A.

Acta Physica Polonica A

2006

vol. 110

issue 3

287-293

Static and dynamic properties of electron spins in self-assembled (In,Ga)As/GaAs quantum dots which contain on average a single electron per dot were studied by pump-probe Faraday rotation. Examples given here are the g-factor tensor components as well as the dephasing time T*_2 within a dot ensemble.

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3 Acta Physica Polonica A

1 2011

1 2006

1 2001

3 Bayer M.

2 Reuter D.

2 Wieck A.

2 Yakovlev D.

1 Bartsch G.

1 Bryja L.

1 Efros A.

1 Forchel A.

1 Greilich A.

1 Jadczak J.

1 Misiewicz J.

1 Oulton R.

1 Plochocka P.

1 Potemski M.

1 Ryczko K.

1 Shabaev A.

1 Stavarache V.

1 Sęk G.

1 Wang T.

1 Wójs A.

1 Yugova I.

1 Zhukov E.

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Influence of Built-in Electric Field on Forbidden Transitions in In_xGa_{1-x}As/GaAs Double Quantum Well by Three-Beam Photoreflectance

Exciton Exchange between Nearly-Free and Acceptor-Bound States of a Positive Trion Assisted by Cyclotron Excitation

Electron Spins in Self-Assembled (In,Ga)As/GaAs Quantum Dots Studied by Pump-Probe Faraday Rotation