Optically detected resonances induced by far infrared radiation in quantum wells and quantum dots

Abstract

Photoluminescence (PL) and optically detected resonances (ODR) where studied on semiconductor quantum wells and quantum dots. Magnetic fields of up to 33 T where applied to samples at temperatures between 0.25 K and 10 K. In nonmagnetic quantum wells optically detected cyclotron resonance was used to determine basic properties such as effective mass and mobility of GaAs/AlGaAs quantum wells. In CdTe/CdMgTe quantum wells evidence for the singlet and triplet state of the negatively and positively charged exciton was found at high magnetic fields. In a highly n-type doped GaAs/AlGaAs quantum well, signatures of the fractional quantum hall effect were observed in PL and ODR data. Also shake up processes in a variety of quantum wells are discussed. In magnetic quantum wells, cusps in the exciton shift are present at moderate magnetic fields which could be assigned to next nearest neighbor interactions between Mn2+ ion pairs and single ions. Resonances in InGaAs/GaAs quantum dots induced by far-infrared radiation have been observed optically. They were studied in quantum dots with different confinement potential and under a series of tilting angles between sample normal and magnetic field direction. The resonances could be assigned to trion formation due to cyclotron resonance in the wetting layer and transitions in the internal energy structure of the dots. Also magnetic CdMnTe/ZnCdTe quantum dots with different Mn content were measured at magnetic fields up to 17 T. At low Mn concentrations a competition between the giant and intrinsic Zeeman splitting leads to a reduction of the polarization of the sample at high magnetic field which makes it possible to determine the Mn content by photoluminescence measurements.