Optical properties of Ho³⁺-, Er³⁺-, and Tm³⁺-doped BaIn₂S₄ and BaIn₂Se₄ single crystals

Abstract

BaIn2S4, BaIn2S4:Ho3+, BaIn2S4:Er3+, BaIn2S4:Tm3+, BaIn2Se4, BaIn2Se4:Ho3+, BaIn2Se4:Er3+, and BaIn2Se4:Tm3+ single crystals were grown by the chemical transport reaction method. The optical energy gap of the single crystals was found to be 3.057, 2.987, 2.967, 2.907, 2.625, 2.545, 2.515, and 2.415 eV, respectively, at 11 K. The temperature dependence of the optical energy gap was well fitted by the Varshni equation. Broad emission peaks were observed in the photoluminescence spectra of the single crystals. They were assigned to donor–acceptor pair recombination. Sharp emission peaks were observed in the doped single crystals. They were attributed to be due to radiation recombination between the Stark levels of the Ho3+, Er3+, and Tm3+ ions sited in C1 symmetry.

Behavior of temperature-dependent photoresponse in unintentional p-type BaIn2Se4 layers through photocurrent spectroscopy

“…These values agree well with the values obtained by measuring optical absorption from BaIn 2 Se 4 crystal by Park et al6 At this time, E g (0) is estimated to be 2.6262, 2.7165, and 2.8672 eV for the transitions corresponding to peaks A, B, and C, respectively. This fact indicates that PC measurement is one of the useful methods for the bandgap determination of the BaIn 2 Se 4 layer.…”

“…But, to be known about the information of BaIn 2 Se 4 is that the bulk of BaIn 2 Se 4 was grown by using the chemical transport reaction method, and its characterization had been investigated through absorption and photoluminescence only. [5][6][7] Moreover, no PC spectroscopy analysis of BaIn 2 Se 4 has been reported yet. In PC measurements, absorbed photons with higher energy than the bandgap energy create electron and hole carriers in the conduction and valence bands, respectively.…”