Photoluminescence and optical absorption spectra of γ₁‐(Ga_xIn_1–x)₂Se₃ mixed crystals

Abstract

Temperature and compositional studies of photoluminescence and optical absorption edge spectra of γ 1 -(Ga x In 1-x ) 2 Se 3 mixed crystals with x = 0.1 -0.4 are performed. Exciton and impurity-related photoluminescence bands are revealed at low temperatures and Urbach shape of the absorption edge is observed in the temperature range 77 -300 K. Temperature and compositional dependences of the photoluminescence band spectral positions and halfwidths as well as optical pseudogap and absorption edge energy width are investigated. Mechanisms of radiative recombination and optical absorption as well as crystal lattice disordering processes in γ 1 -(Ga x In 1-x ) 2 Se 3 solid solutions are studied.

Ellipsometric and Spectrometric Studies of (Ga0.2In0.8)2Se3 Thin Film

“…For a (Ga 0.2 In 0.8 ) 2 Se 3 thin film, 0 < 1 that is the evidence of the strong EPI [26]. It should be noted that, in the thin film, compared to a single crystal [10], the EPI is enhanced (this corresponds to a decrease of the 0 parameter), and the energy of the effective phonon, taking part in the absorption edge formation, practically remains unchanged (Table).…”

“…where (0) and are the energy pseudogap at 0 K and a dimensionless constant, respectively; Θ is the Einstein temperature corresponding to the average frequency of phonon excitations of a system of non-coupled oscillators, and ( ) 0 and ( ) 1 are constants. The obtained (0), , Θ , ( ) 0 , and ( ) 1 parameters for a thin film and a single crystal [10] are given in (7) are shown in Fig. 4 as solid and dashed lines, respectively.…”

“…where is the Urbach energy, is the absorption edge steepness parameter, 0 and 0 are the convergence point coordinates of the Urbach bundle. The parameters 0 and 0 for a (Ga 0.2 In 0.8 ) 2 Se 3 thin film, as well as for a (Ga 0.2 In 0.8 ) 2 Se 3 single crystal [10], are given in Table. The temperature variation of the Urbach absorption edge in a thin film similarly to a single crystal is explained by the electron-phonon interaction (EPI). The insert to Fig.…”

“…For the spectral characterization of the Urbach absorption edge, we used the value of the energy pseudogap ( is the energy position of an exponential absorption edge at a fixed absorption coefficient = 10 4 cm −1 ) which is listed in Table for a thin film (for a single crystal, = 10 3 cm −1 [10]). The temperature dependences of the energy pseudogap and the Urbach energy for a (Ga 0.2 In 0.8 ) 2 Se 3 thin film are presented in Fig.…”

“…The interrelation between photoluminescence and optical absorption spectra were investigated in Refs. [9][10][11]. Refractometric, birefringent and gyrotropic properties of 1 -(Ga In 1− ) 2 Se 3 crystals were studied in Refs.…”