Calorimetric Absorption Spectroscopy of Deep Defects and Quantum Dots

• Authors: R. Heitz , L. Podlowski , J. Böhrer , A. Hoffmann , I. Broser , D. Bimberg
• Languages of publication: EN

Abstracts

EN

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.

Keywords

EN

71.55.Eq; 73.20.Dx; 71.70.Gm

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 1995
• Volume: 88
• Issue: 4
• Pages: 619-630

Dates

published

1995-10

Contributors

author

R. Heitz

• Technische Universität Berlin, Institut für Festkörperphysik, 10623 Berlin, Germany

author

L. Podlowski

• Technische Universität Berlin, Institut für Festkörperphysik, 10623 Berlin, Germany

author

J. Böhrer

• Technische Universität Berlin, Institut für Festkörperphysik, 10623 Berlin, Germany

author

A. Hoffmann

• Technische Universität Berlin, Institut für Festkörperphysik, 10623 Berlin, Germany

author

I. Broser

• Technische Universität Berlin, Institut für Festkörperphysik, 10623 Berlin, Germany

author

D. Bimberg

• Technische Universität Berlin, Institut für Festkörperphysik, 10623 Berlin, Germany