Free excitons at room temperature in cadmium telluride : A photoelectrochemical evidence

Photoelectrochemical experiments with n-type cadmium telluride electrodes are reported. When the semiconductor samples are sufficiently pure and exhibit a low free carrier concentration, the photocurrent vs. photon energy characteristic, at fixed potential, presents an intense and narrow peak which may be correlated to the excitonic absorption of CdTe. A forbidden gap energy value is deduced E_g = 1.475 eV at room temperature.