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HL: Fachverband Halbleiterphysik

HL 53: Optical properties

HL 53.3: Vortrag

Freitag, 29. Februar 2008, 11:00–11:15, EW 201

Spin and energy structure of positively and negatively charged excitons in CdTe/CdMgTe quantum wells subject to strong magnetic fields of 33 Tesla — •Gregor Bartsch¹, Michael Gerbracht¹, Dmitri Yakovlev¹, Manfred Bayer¹, Janneke Blokland², Peter Christianen², and Jan Kees Maan² — ¹Experimentelle Physik II, Technische Universität Dortmund, 44227 Dortmund, Germany — ²High Field Magnet Laboratory, Radboud University Nijmegen, 6525 Nijmegen, Netherlands

Optical studies of energy and spin structure of charged exciton complexes are reported for a 20 nm wide CdTe/CdMgTe quantum well. The sample is modulation p-type doped and contains resident holes, which give rise to formation of positively charged excitons. The type of resident carriers is inverted by above-barrier illumination to the electrons, which allows a comparative study of positively and negatively charged excitons in the same sample. Polarized photoluminescence and reflectivity spectra are measured at temperatures of 0.4 and 4 K and in external magnetic fields up to 33 T. Emission lines of singlet states of these complexes have opposite signs of circular polarization. The binding energy of the positively charged exciton decreases with growing magnetic field, which is qualitatively different from the behaviour of the negatively charged excitons. In high magnetic fields triplet states become bound both for negatively and positively charged excitons.