Optical absorption and urbach tails in layered semiconductor Il{sub}0.999GaPr{sub}0.001Se{sub}2 and TlGaSe{sub}2

摘要

Absorption measurements were carried out on TlGaSe{sub}2 and Tl{sub}0.999GaPr{sub}0.001Se{sub}2 samples in the temperature range of 10-320 K at intervals of 10 K. The phonon energies calculated in TlGaSe{sub}2 and Tl{sub}0.999GaPr{sub}0.001Se{sub}2 are 60.0±5 meV and 55.0±5 meV, respectively. The first defect levels were found to be 2.259 eV, 2.235 eV, 2.200 eV and 2.149 eV for Tl{sub}0.999GaPr{sub}0.001Se{sub}2 at 10 K, 100 K, 200 K and 300 K, respectively. There are abrupt changes in the Urbach energy peaks for Tl{sub}0.999GaPr{sub}0.001Se{sub}2 at 100 K and 200 K. However, there is an abrupt change in the σ{sub}0 values for Tl{sub}0.999GaPr{sub}0.001Se{sub}2 in the temperature ranges of 140-180 K and 220-260 K. These temperatures obtained from the change in Urbach energy and σ{sub}0 values may be phase transition temperatures.