Deep levels induced by CdTe/ZnTe quantum dots

Abstract

The electrical properties of the CdTe/ZnTe quantum dot system have been analyzed to identify deep-level defects related with the presence of quantum dots. The capacitance-voltage (C-V ) and deep level transient spectroscopy measurements were used to investigate the samples. A reference ZnTe sample (without dots) was also studied for comparison. Both samples were grown by molecular beam epitaxy technique on the n-type GaAs substrate. The quantum dots were formed by a Zn-induced reorganization of a thin CdTe layer. The presence of quantum dot formation was confirmed by micro-photoluminescence measurements. The deep level transient spectra for both samples are complex. In order to characterize individual contributions to the deep level transient spectra the latter have been simulated by separated Gaussian components [1]. The results of the deep level transient spectroscopy measurements yield the conclusion that the same defects are present in both materials but there is an increased concentration of the defects in the quantum dot structures. No deep level associated directly with the quantum dot confinement has been identified.