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Ruddlesden-Popper halide perovskites are 2D solution-processed quantum wells with a general formula A2A'n-1MnX3n+1, where optoelectronic properties can be tuned by varying the perovskite layer thickness (n-value), and have recently emerged as efficient semiconductors with technologically relevant stability. However, fundamental questions concerning the nature of optical resonances (excitons or free carriers) and the exciton reduced mass, and their scaling with quantum well thickness, which are critical for designing efficient optoelectronic devices, remain unresolved. Here, using optical spectroscopy and 60-Tesla magnetoabsorption supported by modeling, we unambiguously demonstrate that the optical resonances arise from tightly bound excitons with both exciton reduced masses and binding energies decreasing, respectively, from 0.221 m0 to 0.186 m0 and from 470 meV to 125 meV with increasing thickness from n equals 1 to 5. Based on this study we propose a general scaling law to determine the binding energy of excitons in perovskite quantum wells of any layer thickness. [ABSTRACT FROM AUTHOR]

Modifications of photoluminescence (PL) spectra taken from modulation doped CdTe/CdMgTe quantum well (QW) structures have been studied in magnetic fields up to 45T as a function of 2D electron concentration. [ABSTRACT FROM AUTHOR]

Alloy disorder in II-VI diluted magnetic semiconductors (DMS) is typically reduced when the local magnetic spins align in an applied magnetic field. An important and untested expectation of current models of alloy disorder, however, is that alloy fluctuations in many DMS compounds should increase again in very large magnetic fields of the order of 100 T. Here the authors measure the disorder potential in a Zn0.70Cd0.22Mn0.08Se quantum well via the low temperature photoluminescence linewidth using a pulsed magnet system to ∼89 T. Above 70 T, the linewidth is observed to increase again, in accord with a simple model of alloy disorder. [ABSTRACT FROM AUTHOR]

A thin AlGaAs barrier (2.5 nm) inserted into a GaAs/AlGaAs single heterojunction formed a square and a wedge-shaped triangular quantum well in the conduction band. In such a structure, the valence band does not have tunnel-coupled energy levels. Hence, the photogenerated valence holes tend to move to the GaAs flatband region. This asymmetric quantum structure showed intense nonlinear photoluminescence emission behavior with external excitation power and magnetic field. Increasing the external laser power simply caused the number of photogenerated holes to increase near the interface close to the quantum well, which then recombined with the conduction band electrons. External magnetic fields resulted in an increased Coulomb attraction which generated dynamic movement of valence holes. The migration of unbound holes to the interface region from the GaAs flatband area produced highly nonlinear optical transitions in magnetic fields. [ABSTRACT FROM AUTHOR]