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Electron effective mass (m[sub e][sup *]) in GaN[sub x]As[sub 1-x]/GaAs quantum wells (QWs) is investigated by the optically detected cyclotron resonance technique. The m[sub e][sup *] values of 0.12m[sub 0] and 0.19m[sub 0] are directly determined for the 70-Å-thick QWs with N composition of 1.2% and 2.0%, respectively. This sizable increase in the electron effective mass is consistent with the earlier theoretical predictions based on the strong interaction of the lowest conduction band states with the upper lying band states or impurity band induced by the incorporation of N. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Magneto-optical spectroscopy in combination with tunable laser spectroscopy is employed to study the effect of sample design on optical spin-injection efficiency from a Zn(Cd)MnSe diluted magnetic semiconductor (DMS) into non-magnetic CdSe quantum dots (QDs). Two samples with inverted growth sequence of the DMS and QD layers were grown for this purpose. Despite observation of clear evidence for exciton/carrier-injection from the DMS to the QDs in both structures, their spin-injection efficiency is markedly different. The structure grown with the QD layer topmost exhibits rather efficient spin-injection, while the structure grown with the DMS layer topmost does not show any sign of spin-injection. Even in the former case, the spin-polarization of the injected excitons/carriers is deduced to be about 32%, decreasing from 100% before the injection. The observed spin loss is shown to occur during the spin-injection across the heterointerfaces. [Copyright &y& Elsevier]

Abstract: Metamorphic InGaAs quantum well structures grown on GaAs reveal strong light emission at 1.3–1.6 μm, smooth surface with an average roughness below 2 nm and good rectifying I–V characteristics. Dark line defects are found in the QW. Post growth thermal annealing further improves the luminescence efficiency but does not remove those dark line defects. Some challenges of epitaxial growth using this method for laser applications are discussed. [Copyright &y& Elsevier]

Abstract: Dynamics of spin injection has been studied in double quantum wells (DQWs) composed of diluted magnetic and non-magnetic semiconductors. Picosecond-transient photoluminescence (PL) of excitons in the DQWs has been measured in magnetic field. In the Cd1− x Mn x Te-based DQWs, the PL intensity of the magnetic well (MW) excitons decays faster with decreasing barrier width from 12 to 2nm. This provides the evidence for carrier tunneling from the MW to the non-magnetic well (NW) through the barrier layer. The degree of circular polarization in the transient PL of the NW exciton in magnetic field shows marked evidence for spin injection and rapid spin relaxation in the DQW system. In the Zn1− y Mn y Se-based DQWs, the degree of circle polarization in the NW exciton PL at 3T shows a rise with a time constant of 400ps, while the PL of the MW exciton decays within 50ps. The observed result is interpreted by the individual spin injection for electrons and holes from the MW to the NW. The results of the transient PL of excitons in the DQWs are compared with the transient absorptions of excitons studied by the pump-and-probe spectroscopy. [Copyright &y& Elsevier]

Type I band line-up in GaNxAs1−x/GaAs multiple quantum wells (MQW) with x⩽3% is concluded based on the following experimental results: (i) a comparable radiative decay time of the GaNAs-related photoluminescence (PL) measured from single GaNAs epilayers and the GaNAs/GaAs MQW structures, (ii) the observed PL polarization, and (iii) the spatial confinement of photoexcited holes within the GaNAs layers under resonant excitation of the GaNAs MQW. [Copyright &y& Elsevier]

Magneto-photoluminescence (PL) has been studied in type II Zn1−xMnxSe/ZnSySe1−y multiple quantum wells (QWs) with the Mn content x between 0.03 and 0.15. Two PL lines are observed in the samples with x equal to 0.05 and 0.15. The lines are attributed to the excitons of two different types, coexisting in the QWs. At least one of them is associated with the formation of an exciton magnetic polaron. [Copyright &y& Elsevier]