Does the low-temperature Arrhenius plot of the photoluminescence intensity in CdTe point towards an erroneous activation energy?

Several experimental photoluminescence (PL) bands of different energies for variously prepared CdTe samples are compared. Temperature variation of the PL intensity is modeled with two nonradiative thermal activation energies, of which $E_{\mathrm{T1}}$ is dominant for about T⩽60 K, and $E_{\mathrm{T2}}$ for the upper temperature range of the measurement. The size of $E_{\mathrm{T1}}$ is invariably of the order of a few meV and, although of unclear origin, its magnitude is usually interpreted as an electronic energy level difference over which the carriers escape by thermal excitation. In CdTe the existence of such a small energy level difference $E_{\mathrm{T1}}$ is not easy to explain. On the contrary, we find clear evidence that, at low temperature, the PL intensity reduction with increasing temperature in fact results from the approximately $T^{\text{−2}}$ temperature dependent capture cross sections of the carriers at the recombination centers, and not from a genuine thermal activation energy $E_{\mathrm{T1}}.$