Excitation-Power Dependence of Free Exciton Photoluminescence of Semiconductors

We have derived an analytical formula for the excitation-power dependence of the free exciton photoluminescence (PL) intensity. It has been found that the PL intensity I depends on the power of the excitation laser L as I ∝ L k , where k is the power index. We have deduced the analytical formula that describes the value of k for the free exciton PL emission under the above-band-gap excitation conditions. The results indicate that the value of k is in the region of 1< k <2 depending on both the value of L and material properties such as radiative and competitive nonradiative recombination probabilities.