Radiative Lifetime of Wannier—Mott Excitons in Nanoclusters of Semiconductors with Direct- and Indirect Band Structures

We calculate the radiative lifetime of Wannier—Mott excitons in potential wells formed by nanoclusters of narrow-band semiconductors in wide-band materials. Examples of semiconductor nanoclusters with both direct and indirect band structures (InAs and diamond, respectively) are analyzed. It is shown that in the case of nanoclusters of direct-band semiconductors the radiative lifetime of the Wannier—Mott excitons in them is determined by recombination of the electrons and holes, which form the excitons, without participation of phonons, and increases significantly as the cluster size decreases. In the case of nanoclusters of indirect-band semiconductors, the radiative lifetime of the Wannier—Mott excitons in them is determined by recombination of the electrons and holes, which form the excitons, with simultaneous radiation of phonons and is weakly dependent on the cluster size. The effect of the increase in the radiative lifetime of the Wannier—Mott excitons in nanoclusters of direct-band semiconductors with a decrease in their dimensions can be used in various exciton experiments, which require comparatively great time resources.