Decay Characteristics of Photoluminescence Lines in CuGaS ₂ Crystals

Abstract

Time-resolved photoluminescence (PL) measurements have been carried out for CuGaS2 single crystals with a slightly Cu-rich composition grown by an iodine transport method. PL lines at 2.460 eV, 2.457 eV, 2.417 eV, 2.404 eV, 2.397 eV and 2.295 eV exhibited biexponential decay. The relationship between the decay time of the fast component (τ f ) and the localization energy (E loc) can be given by τ f ∝E loc 1.25. On the other hand, the decay times of the slow components (τ s ) have been classified into two groups having different trends τ s ∝E loc 2.7 and E loc 0.5. The difference between the two groups is discussed in terms of native defects and the iodine impurity included in the luminescence centers.

Resonance impurity radiation in CuGaS2 crystals

“…The bands C 1 (2.4584 eV) and C 2 (2.4561 eV) presented in Fig. 3 may be analogues of bands H (2.457 eV), H * (2.460 eV) revealed by the authors of the work [16]. The band I a (2.501 eV) in the work [16] is attributed to bound excitons.…”

“…3 may be analogues of bands H (2.457 eV), H * (2.460 eV) revealed by the authors of the work [16]. The band I a (2.501 eV) in the work [16] is attributed to bound excitons. According to the above given data and the results reported in the works [18,19], the band at the energy 2.501 eV is determined by free excitons, namely by the transverse mode of the C 4 exciton polariton.…”

“…The found radiation spectra are caused by the excitons bound on neutral donor (acceptor). In work [16] the lines 2.495 eV (I b ), 2.493 eV (I c ) are found, being apparently analogues of lines L 1 and L 2 shown in Fig. 3.…”

“…This compound belongs to the chalcopyrite group with space group D 12 2d [9][10][11][12]. In these crystals resonance Raman scattering of exciton polaritons [13][14][15][16][17], interference of additional exciton waves, spatial dispersion of exciton polaritons [18][19][20] and biexciton radiation [21] are found.…”

“…The polariton radiation of the C 4 exciton was found and the Raman scattering under the excitation with various laser lines which energy exceeds the longitudinal exciton energy was investigated [9][10][11][12]. A series of narrow lines attributed to bound excitons was found in the long-wave region from the transverse exciton frequency [13][14][15][16]. However, the bound excitons have not been studied in detail and the structure of zero phonon lines and their replicas have not been revealed.…”