Cyclotron Resonance in the 2D Hole Gas of GaAs/AlGaAs Heterostructures

Magneto-optical spectroscopy in the far infrared is a valuable tool to study the energetic structure close to the extrema of the energy bands. In heterostructures like GaAs/AlGaAs the valence band structure is very complex due to the strong electric field near the interface and the lack of inversion symmetry. As a consequence the light hole band is split off the heavy hole band which is highest in energy. Also the spin degeneneracy is lifted for k ≠ 0 and there exists a strong mixing between states of different spin orientation. States mainly consisting of heavy hole states with spin-up are called a-states, whereas states mainly consisting of heavy hole states (hh) with spin-down are called b-states [1,2]. Transitions may occur between states of the same spin orientation (na → ma, n, m = 1,2,…, kb → lb, k,1 = −2,−1,0,1,…). but also between states with different spin orientation (CSR — Combined Spin flip Resonances). For the assignment of the experimentally observed absorption peaks to transition energies the energetic position of the Landau states as a function of the magnetic field was calculated.