Electroreflectance Observation of Transformation Processes of the First and Second Minibands to Wannier–Stark Localization States in a GaAs/AlAs Superlattice

概要

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We have investigated the transformation processes of the first ($n=1$) and second ($n=2$) minibands to the Wannier–Stark (WS) localization states in a GaAs (6.8 nm)/AlAs (0.9 nm) superlattice embedded in a $ p$–$i$–$n$ structure by electroreflectance spectroscopy. The high sensitivity of electroreflectance enabled us to observe the interband optical transitions associated with the $n=2$ minibands in addition to those associated with the $n=1$ minibands. The systematic results of the electroreflectance spectra as a function of electric field strength demonstrate that the electric field strength for the formation of the WS-localization state of the $n=2$ miniband is higher than that of the $n=1$ miniband, which reflects a difference in the energy widths of the $n=1$ and $n=2$ minibands. The experimental results are quantitatively discussed on the basis of the electric-field-strength dependence of the energies and envelope functions of the $n=1$ and $n=2$ minibands calculated using a transfer-matrix method. We find a clear correlation between the miniband widths and the critical electric field strengths for the formation of the WS-localization states.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2005-12-15