Anisotropic photoluminescence of β-LiGaO2 crystal

Abstract

Manifestation of the anisotropic properties of β-LiGaO2 crystal revealed in photoluminescence (PL) excitation and emission has been studied. Three exciton bands at 6.043, 6.085 and 5.980 eV, corresponding to three crystallographic axes, have been found in the PL excitation spectrum under the synchrotron irradiation, whose relative contribution depends on crystal orientation. Study of the properties of polarized luminescence 4.43 eV under the excitation with ArF laser (193 nm) with varied intensity in the 10–300 K temperature range has demonstrated that the excitation-induced and temperature-induced band's energy and intensity behaviour depends on the orientation of the crystal in relation to the incident light. The simultaneous coexistence of two radiative processes is proposed for the explanation of the PL properties of β-LiGaO2 crystal: the tunnel recombination of donor-acceptor pairs (DAP) and the recombination of a free electron with an acceptor center (e-A). An assumption is done about the complex nature of the 4.43 eV emission band consisting of subbands corresponding to the DAP radiative recombination in three crystallographic directions, and a subband due to the e-A radiative recombination. Dependence of the luminescence thermal quenching properties on excitation density are discussed.