The effects of carrier thermal escape and retrapping on the temperature dependence of the photoluminescence of InAs/GaAs self-assembled quantum dots are investigated. A systematic experimental study of the temperature evolution of the photoluminescence spectra in two different sets of samples is reported. The photoluminescence behavior is well reproduced in terms of a steady state model for the carrier dynamics which takes into account the quantum-dot size distribution, random population effects, and carrier capture, relaxation, and retrapping. The relative contributions of these processes to the photoluminescence thermal quenching is discussed.

We report, for the first time, ballistic magnetoresistance effects in a two-dimensional electron gas (2DEG) subjected to a spatially modulated periodic magnetic field. The periodic magnetic field is formed by the presence of superconducting stripes on the surface of the heterostructure with a 2DEG. We observe oscillatory magnetoresistance due to a commensurability effect between the classical cyclotron diameter and the period of magnetic modulation. The behavior is in agreement with existing theory with no adjustable parameters.

We describe a low‐noise scanning Hall probe microscope having unprecedented magnetic field sensitivity (∼2.9×10⁻⁸ T/√Hz at 77 K), high spatial resolution, (∼0.85 μm), and operating in real‐time (∼1 frame/s) for studying flux profiles at surfaces. A submicron Hall probe manufactured in a GaAs/AlGaAs two‐dimensional electron gas (2DEG) is scanned over the sample to measure the surface magnetic fields using conventional scanning tunneling microscopy positioning techniques. Flux penetration into a high T_c YBa₂Cu₃O_7−δ thin film has been observed in real time at 85 K with single vortex resolution. Flux is seen to enter the film in the form of vortex bundles as well as single flux quanta, Φ₀.

We describe a novel magnetotunneling spectroscopy technique for probing the complicated dispersion curves of hole states in the quantum well of p-type double-barrier resonant-tunneling structures. Strong mixing between light- and heavy-hole states is observed. Some of the states clearly exhibit a negative hole effective mass for motion in the plane of the quantum well.

We report on the magnetoresistance of a two-dimensional electron gas subjected to an abrupt magnetic field gradient arising from a ferromagnetic stripe fabricated at its surface. A sharp resistance resonance effect is observed at $B_p$ due to the formation of two types of magnetic edge states that drift in opposite directions perpendicular to the magnetic field gradient for $B<\mathrm{}{B}_p$ and $B>\mathrm{}{B}_p$. A semiclassical drift-diffusion model gives a good description of the effects of the magnetic confinement on both the diagonal and off-diagonal components of the resistivity tensor.