Temperature dependence of terahertz optical characteristics and carrier transport dynamics in p-type transparent conductive CuCr_{1- x}Mg_xO₂ semiconductor films

Terahertz reflectance spectra and electrical transport of CuCr _1-xMg_xO₂ films have been studied in temperature range of 150-300 K. With increasing temperature, the phonon mode near 15 THz shows a redshift trend, and free carrier absorption below 6 THz becomes more prominent. Moreover, hole effective mass increases linearly from 0.028 to 0.48 m₀ with the temperature and composition. Hall coefficient shows a turning-point at about 220, 206, and 194 K for the composition of x 0.02, 0.06, and 0.10, respectively. The phenomena can be attributed to the transition of carrier transport mechanism from a thermal activation behavior to a variable range-hopping one.