Optically detected cyclotron resonancein a single GaAs/AlGaAs heterojunctionDissertationpresented to the Faculty of Physics of theTechnische Universit¨at Dortmund, Germany,in partial fulfillment of the requirementsfor the degree ofDoktor rer. nat.presented byGregor BartschDortmund, August 2011Accepted by the Faculty of Physics of theTechnische Universit¨at Dortmund, Germany.Day of the oral exam: 23rd September 2011Examination board:Prof. Dr. Dmitri YakovlevProf. Dr. Manfred BayerProf. Dr. G¨otz UhrigDr. Ilya AkimovContents1 Introduction 32 Cyclotron resonance - basic principles 72.1 Quantum mechanics . . . . . . . . . . . . . . . . . . . . . . 72.1.1 The effective mass approximation . . . . . . . . . 72.1.2 External magnetic fields . . . . . . . . . . . . . . . 92.1.3 Far-infrared radiation . . . . . . . . . . . . . . . . . 142.1.4 Kohn’s theorem . . . . . . . . . . . . . . . . . . . . 152.2 The classical Drude model . . . . . . . . . . . . . . . . . . 173 Optical transitions 213.1 GaAs band structure . . . . . . . . . . . . . . . . . . . . . 213.2 Transition-matrix elements . . . . . . . . . . . . . . . . . 233.3 Excitons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 Experimental setup 274.1 FIR transmission . . . . . . . . . . . . . . . . . . . . . . . . 274.2 FIR-ODCR . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 The sample 315.1 The high-mobility single heterojunction . . . . . . . . . 315.