Temperature dependance of the fundamental absorption edge in CdTe

Optical measurements made on CdTe put in light an extrinsic transition previously used to determine the interband edge of this compound. The donor level involved has a depth of 30 meV inside the bandgap at 77°K and of 60meV at 300°K. The value obtained for its temperature coefficient, suggests an association of this level with the L minimum of the conduction band.Also, determined is the true optical bandgap of CdTe between many conflicting results. One obtains: E_g = 1.529 meV with a temperature coefficient of ?3.10^?4eV/°K.