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Determination of Quantum Dot Morphology from Magnetooptical Properties

100%

Křápek V., Schliwa A., Bimberg D.

Acta Physica Polonica A

2007

vol. 112

issue 2

339-343

We present here the calculations of magnetooptical properties in InAs/GaAs quantum dots with different shapes, including excitonic effects. The influence of several structural parameters, such as vertical profile, aspect ratio, and basis squareness is discussed, as well as the possibility to retrieve the structural parameters from magnetooptical measurements.

Calorimetric Absorption Spectroscopy of Deep Defects and Quantum Dots

76%

Heitz R., Podlowski L., Böhrer J., Hoffmann A., Broser I., Bimberg D.

Acta Physica Polonica A

1995

vol. 88

issue 4

619-630

In recent years calorimetric absorption spectroscopy has been developed to a powerful tool of semiconductor spectroscopy based on the detection of nonradiative relaxation processes. Calorimetric absorption spectroscopy is an ultrasensitive quantitative absorption technique. Recent investigations of Fe in III-V semiconductors and of InAs/GaAs quantum dots are presented here to illustrate the potential of the method. Sharp absorption lines are observed at the low energy onset of the Fe^{3+/2+} charge transfer band in III-V semiconductors. Calorimetric absorption spectroscopy measurements in the mK range reveal a strong temperature dependence of their absorption strength identifying unambiguously Fe^{3+}(^{6}A_{1}(S)) as a ground state. The excited state is attributed to (Fe^{2+},h). The importance of exchange interaction for the observed fine structure is pointed out and binding energies are determined. The quantum yield of the intracenter ^{5}Τ_{2}-^{5}E transition of F^{2+} is determined to be below 50% at 2 K. A correlation between the nonradiative relaxation rate and the isotope splitting of the ^{5}Τ_{2}-^{5}E transition is observed, demonstrating the crucial role of the dynamical Jahn-Teller coupling of the ^{5}Τ_{2} state to local Τ_{2} modes for the multiphonon relaxation process. Quantum dots having a d-function density of states should exhibit no Stokes shift between absorption and emission as observed for one- and two-dimensional systems. Calorimetric absorption spectroscopy demonstrates ground state absorption coinciding in energy with the luminescence for self- organized InAs/GaAs quantum dot structures grown by MBE. Transitions into excited hole states are resolved and a comparison to photoluminescence excitation spectroscopy is presented.

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2 Acta Physica Polonica A

1 2007

1 1995

2 Bimberg D.

1 Broser I.

1 Böhrer J.

1 Heitz R.

1 Hoffmann A.

1 Křápek V.

1 Podlowski L.

1 Schliwa A.

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Determination of Quantum Dot Morphology from Magnetooptical Properties

Calorimetric Absorption Spectroscopy of Deep Defects and Quantum Dots