Ch. Uihlein

Observation of oscillatory linewidth in the cyclotron-resonance of GaAs-AlxGa1-xAs heterostructures

Abstract The linewidth of the far infrared cyclotron resonance in the 2-D electron gas in GaAs-AlxGa1−xAs heterojunctions show oscillations between 0.070 and 0.32 T as a function of the resonance magnetic field at 5 K. With increasing temperature the maximum linewidth decreases, whereas the minimum increases. This oscillatory behavior is shown to be correlated with the filling factor of the Landau levels.

Hybrid cyclotron-intersubband resonance in thin InAs layers confined between GaSb

Abstract In a heterostructure of InAs confined between GaSb, measurements of far infrared transmission as a function of the magnetic field and its orientation demonstrate the formation of hybrid subbands due to electric and magnetic quantization. The observed energies of resonant transitions with the magnetic field parallel to the layer plane are in quantitative agreement with those calculated theoretically.

Quantum transport in GaAs doping superlattices

The resistance of the n channels in GaAs doping superlattices shows clear oscillations as a function of the magnetic field, and varies with the voltage applied between the n and the p layers and with the orientation of the magnetic field with respect to the doping layer plane. These experimental results are analyzed in terms of the two‐dimensional conductivity of the system, and the subband separation is derived from a comparison between the measurements and model calculations.

Quantum transport of electrons confined in a thin GaAs layer by an impurity space charge potential in high magnetic fields

Abstract The resistance of a thin, n-doped, GaAs layer sandwiched between p-doped layers shows clear quantum oscillations as a function of the magnetic field which depend on the orientation of the magnetic field with respect to the layer plane. The data for parallel and perpendicular magnetic fields are analyzed in terms of two dimensional conductivity using a simple model and the subband structure is deduced consistently from both experiments.

Oscillations of the cyclotron resonance linewidth with landau level filling factor in GaAs/AlGaAs heterostructures

Abstract The linewidth of cyclotron resonance in a 2D electron gas in GaAs/AlGaAs heterojunctions shows oscillations between 0.070 T and 0.32 T as a function of the resonance magnetic field at 5 K. With increasing temperature the maximum linewidth decreases, whereas the minimum increases. This oscillatory behaviour is shown to be correlated with the filling factor of Landau levels.

High Magnetic Field Zeeman Splitting and Anisotropy of Cr-Related Photo-Luminescence in Semi-Insulating GaAs and GaP

The famous 0.84 eV photoluminescence structure arising from recombination at Cr-related defects in GaAs is studied using high resolution Zeeman spectroscopy with magnetic fields up to 10 T. The Zeeman anisotropy for B in the (Oil) and (001) planes is measured. From these results the defect is shown to have a dominant trigonal ((111)-axial) perturbation together with a weaker tetragonal Jahn-Teller distortion. The initial and final states of the photoluminescence are described in terms of a simple effective Hamiltonian which can explain all the essential features of the observed Zeeman splitting and anisotropy. In contrast with GaAs, the Zeeman data for the 1.03 eV photoluminescence observed in GaP(Cr) corresponds to defects with (100) axial symmetry. Posssible reasons for this difference are discussed.

Investigation of bandmasses and g-values by two-photon-magneto-absorption (TPMA) in ZnSe

Abstract We present the first TPMA-measurements (up to 9T) on the 24 fold degenerate 2p-exciton in ZnSe. The measurements were carried out in Faraday- ( k ‖ B ) and Voigt-configuration ( k ⊥ B ). By various combinations of polarization states of the two fundamental beams (σ+,σ-;σ,π) one can selectively excite excitons with total angular momentum Mtot=O,± and ±2. From the large splitting due to the envelope g-value and from the strong diamagnetic shift we can deduce a reliable set of conduction (m∗e,gc) and valence band parameters (γ1,γ2,γ3,κ). The detailed calculation of these parameters is based on the theory of Lipari et al. using irreducible tensor operators.

Zeeman spectroscopy of cobalt doped InP

Abstract The 785.8 meV crystal field 4 A 2 (F) - 4 T 1 (F) transition of Co 2+ in InP is studied in magnetic fields from 0 to 10 T. Clear C 3V axial symmetry is found and is attributed to a strong dynamic Jahn-Teller effect in the 4 T 1 (F) excited state. A ground state g-value of 2.10 ± 0.10 and excited state g-values of g ‖ = 0.96 ± 0.05, g ⊥ = 3.76 ± 0.05 are found.

Cyclotron resonance of 2D electrons in GaAs/AlxGa1−xAs heterostructures at low densities

Cyclotron resonance of the two‐dimensional (2D) electron gas in GaAs/AlGaAs heterostructures is studied as a function of the far infrared laser energy at different temperatures. The effective mass, determined from the resonant magnetic field, agrees very well with the values obtained in bulk GaAs. In samples of very low carrier density the linewidth of cyclotron resonance shows pronounced oscillations at He temperatures. A comparison with Shubnikov–de Haas measurements demonstrates that these oscillations are correlated with the filling factor of Landau levels. In samples of slightly higher carrier density ns >3×1011/cm2 the linewidth becomes almost independent of magnetic field.

Resonant Raman scattering at the indirect triplet exciton in AgBr in high magnetic fields

Abstract Resonant two-phonon Raman scattering involving the indirect triplet exciton is studied in AgBr at T = 1.8 K and magnetic fields up to 20 Tesla. By a quantitative analysis of the scattered 2TO(L) intensity we are able to determine the symmetry of hole states to be L - 4,5 , the exchange splitting Δ = 0.17 meV and effective g-values of g c = 1.46 and g ″ v = 2.61 for electrons and holes. The observed diamagnetic shifts lead to a value of 32 meV for the exciton binding energy.