Molecular beam epitaxy, photoluminescence from Mn2+ multiplets and self-trapped exciton states of γ-MnTe single-crystalline thin films

• ZB-MnTe thin films are epitaxially grown by MBE in spite of the metastable nature. • High-crystalline quality, atomic surface flatness and sharp interface are yielded. • PL emissions of 4 T 1g ( 4 G ) and 4 T 1 ( 4 G ) related to Mn 2+ d - d multiplets are observed. • Two extra PL transitions attributed to STE states are demonstrated below T N . • Dynamics of photoexcited d -electrons are strongly correlated to the AFM transition. Single-crystalline γ -MnTe thin films with zinc-blende structure were grown epitaxially on InP(111) by molecular beam epitaxy. Two-dimensional growth regime and atomic surface flatness are achieved, and appearance of Laue’s oscillation peaks illustrates the superior crystalline quality and interface of γ -MnTe films. A pseudocrystal buffer layer is formed at interface releasing the strain led by the large lattice mismatch between γ -MnTe and InP, and then growth of γ -MnTe films with a perfect lattice evidences the high-quality crystallinity in a fully relaxed state. Photoluminescence (PL) emissions from 4 T 1g ( 4 G ) and 4 T 1 ( 4 G ) related to Mn 2+ ions d - d multiplets are observed with their respective activation energies of ∼142.5 meV and ∼323.5 meV. Such high potentials reflecting the nonradiative recombination indicate the thermal stability of these PL. Moreover, two extra PL transitions assigned to be the emissions from self-trapped exciton (STE) states are found below T N . Time-resolved PL (TRPL) spectra at various temperatures indicate that the relaxation dynamics of photoexcited d -electrons is strongly correlated to the antiferromagnetic ordering transition due to the synergy of magnon, phonon and STE states. These findings suggest that introduction of STE states in a material by controlling its magnetic ordering qualifies the competition in optoelectronics devices.