Excitonic Molecule Transitions in ZnO

Abstract

Abstract By means of excitation spectroscopy, the M‐band emission in ZnO is identified to be mainly due to decay of excitonic molecules (EM) into longitudinal B excitons and upper B polaritons. The latter process is easily stimulated and gives rise to a band (M 2 ) of positive optical gain. Formation of EM by two‐photon resonance absorption and by induced absorption is observed in excitation spectra as well as directly in transmission. From the experiments the EM energy is deduced to E M = 6.740 eV.