Ground and Excited States of the Biexciton and the M‐Band Luminescence in Highly Excited ZnO

Additional measurements on polarization properties and excitation intensity dependence are presented for the resonant two‐photon Raman scattering via biexcitons in highly excited ZnO at low temperatures reported earlier [1]. The binding energy of the biexciton ground state (symmetry Λ 1 ) is determined to (19 ± 0.2) meV. An excited biexciton state (symmetry Λ 5 ) is observed for the first time in II‐VI compounds. Moreover, the excitation spectra of the M‐band and of the bound exciton I 9 are given for different polarizations of the exciting light. They indicate that the M‐band can be ascribed to a superposition of extrinsic and intrinsic recombination processes.