Time-resolved photoluminescence lifetime measurements of the Γ_(5) and Γ_(6) free excitons in ZnO

摘要

Time-resolved photoluminescence spectroscopy at 2 K was used to measure the radiative recombination lifetime of the allowed (Γ_(5)) and forbidden (Γ_(6)) free excitons in ZnO. The measurements were made on a sample containing internal strain, which altered the sample symmetry, and resulted in relaxed selection rules, allowing theΓ_(6) exciton to be observed. A radiative recombination lifetime of 259 ps was measured for the Γ_(5) exciton and 245 ps for the Γ_(6) exciton. The decay of the free excitons was of single-exponential form, and the decay times were obtained using a least-squares fit of the data.