Abstrakt
The optical absorption edge of bulk CdTe single crystal was measured by infrared transmission under saturated Cd pressure in the temperature interval 295-1223 K. The absorption coefficient was directly determined up to the value of 100 cm(-1).
For higher values, it was estimated by extrapolating the spectra according to the Urbach exponential rule. It was observed that the common temperature-independent intersection of extrapolated Urbach absorption edge, the "Urbach focus," does not exist in CdTe.
The temperature dependence of band-gap energy E-g defined by E-g(300 K) = 1.518 eV and dE(g)/dT = - 4.4 x 10(-4) eV/K was established, postulating linear temperature dependence of E-g by fitting the temperature dependent absorption coefficient at the band edge alpha(g)(T) = 6600 - 4T (K) (cm(-1)).