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Shallowly formed InAs quantum dots (QDs) embedded in GaAs are investigated by Optically Detected Microwave Resonance (ODMR) technique. The low temperature (1.6 K) photoluminescence (PL) spectrum reveals a two-peak structure which is attributed to two different classes of QDs: smaller and larger in size. V-band (60 GHz) ODMR is selectively detected in each of the peaks and depending on the PL detection energy, a different ODMR spectrum is obtained. Detection in the high-energy band reveals a low-field negative signal which is ascribed to cyclotron resonance of the electron in the two-dimensional wetting layer, corresponding to an effective mass of 0.067 m 0. The microwave-induced signal at higher fields (~1.1 T) is tentatively attributed to magnetic resonance transitions between spin states of the holes confined in the smaller QDs. When monitoring the emission of the larger QDs, the obtained microwave-induced signal is negative while the resonance line at low field, associated with the cyclotron resonance, is no longer present. The V-band ODMR spectra are compared with W-band (94 GHz) measurements obtained for the same QD structure.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
