Plots of the square of the absorption coefficient α 2 vs photon energy E for AgGaSe2 at T = 15, 80, 200, and 300 K for (a) E ⊥ c and (b) E ‖ c.
(a) Plots of E g vs T for E ⊥ c (solid circles) and E ||c (open circles) determined from the optical absorption measurements. The solid line represents the fit of the experimental E g data to Eq. (3) . The dashed line indicates dE g/dT data for E ⊥ c. (b) Plots of ΔE g = E g(T) − E g(0) vs T for AgGaSe2, together with those for ΔE th (red line) and ΔE ph (blue line) calculated from Eqs. (4) and (6) , respectively. The open squares indicate the calculated ΔE th results by the first-principle band calculation.
PR spectra for AgGaSe2 measured at T = 20–300 K for (a) E ⊥ c and (b) E ‖ c.
PR spectra for AgGaSe2 measured at T = 20 K for E ⊥ c (solid circles) and E ‖ c (open circles). The solid lines represent the fits using Eq. (8) with n = 2 to the experimental data.
Plots of (a) E 0 B , (b) E 0 A , and (c) E 0 C vs T determined from the PR measurements (solid circles). The solid lines represent the fit of the experimental data to Eq. (3) . The dashed lines indicate dE 0 α /dT (α = A, B, C) data.
Valence-band splitting at the Γ point of (a) CuInSe2 and (b) AgGaSe2. The selection rules of the optical dipole transitions are schematically shown.
(a) Plots of Δcr vs T for AgGaSe2 determined from the PR measurements. The solid line represents the calculated result of Eq. (14) . (b) Plots of Δso vs T for AgGaSe2.
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