Photoluminescence in EuS-PbS-EuS semiconductor structures with double ferromagnetic barrier

The temperature, magnetic field, and laser excitation power dependences of photoluminescence (PL) were studied in 5×(EuS (5.5 nm)–PbS (17.5 nm)) semiconductor ferromagnetic multilayers grown epitaxially by high vacuum deposition on a BaF2 (111) substrate. In EuS–PbS heterostructures, ferromagnetic layers of EuS form electron barriers for both electrons and holes in nonmagnetic quantum wells of PbS. PL was observed in the near infrared due to electronic transitions in PbS quantum wells with narrow energy gaps. Measurements carried out at 4.2 and 77 K (i.e., below and above the Curie temperature of EuS layers, which is about 14 K) showed characteristic PL spectra consisting of one or two lines with a strongly non-linear response upon increasing the YAG laser excitation power. Below the Curie temperature, the application of a weak magnetic field of 200 Oe results in a change of the PL intensity as well as a small red shift in the PL energy of about 1 meV. These observations are discussed in terms of the model taking into account the magnetization-dependent height of the EuS potential barrier for electrons in a PbS quantum well.