The Nature of Potential Fluctuations in the MBE CdTe/CdMgTe Quantum Well in a Magnetic Field: Experiment and Theory

M. Szota, b, K. Karpierza, A.A. Avetisyanc, A.P. Djotyanc, J. Kossutb and M. Grynberga aInstitute of Experimental Physics, Warsaw University, Hoża 69, Warsaw, Poland bInstitute of Physics, Polish Academy of Sciences, al. Lotników 32/46, Warsaw, Poland cDepartment of Physics, Yerevan State University, Yerevan, Armenia

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Received: 17 06 2006;

Far infrared photoconductivity spectra of CdTe/Cd0.8Mg0.2Te quantum well uniformly n-type doped with iodine in barriers and in the well were investigated as a function of the magnetic field. The spectra were recorded for several fixed far infrared photon energies and peaks corresponding to intra donor transitions were observed. The magnetic field at which the peaks were observed was the same for all far infrared photon energies used. This is interpreted as an evidence of the presence of fluctuations of the electrostatic potential - quantum dots which reduce the dimensionality of the potential in which a shallow donor is placed. A characteristic size of the fluctuations was found to be of 23-25 nm and 30-40 nm. Theoretical calculations show a nonmonotonic dependence of the electron binding energy on the donor centre in such quantum dot, as a function of magnetic field. This explains why the position of experimentally observed peak is insensitive to far infrared photon energy used. Temperature evolution of spectra and the theoretical model proposed, indicate similarities between fluctuations in the two-dimensional structure investigated and fluctuations in bulk systems.

DOI: 10.12693/APhysPolA.110.379 PACS numbers: 71.55.Gs, 72.15.Rn, 72.80.Ey, 73.21.Fg