Magneto-optical properties of bound excitons in ZnO

We present results of magneto-optical measurements and theoretical analysis of shallow bound exciton complexes in bulk ZnO. Polarization and angular dependencies of magnetophotoluminescence spectra at 5 T suggest that the upper valence band has Γ₇ symmetry. Nitrogen doping leads to the formation of an acceptor center that compensates shallow donors. This is confirmed by the observation of excitons bound to ionized donors in nitrogen doped ZnO. The strongest transition in the ZnO:N (I₉ transition) is associated with a donor bound exciton. This conclusion is based on its thermalization behavior in temperature-dependent magnetotransmission measurements and is supported by comparison of the thermalization properties of the I₉ and I₄ emission lines in temperature-dependent magnetophotoluminescence investigations.