Stoichiometric effect on the defect states and optical properties of LiInSe single crystals.

LiInSe crystals are promising semiconductor materials for neutron detectors due to the large neutron capture cross-sectional area of the specific isotopes (Li) and high charge transport properties. However, the optoelectronic performance fails to reach the expected level due to the difficulty of controlling the crystal defects. Herein, we modulate the stoichiometric ratio to control the type of defects in single LiInSe crystals grown by the vertical Bridgman method. The UV‒vis-NIR transmission results indicate that the band gap of the yellow colored LiInSe sample is close to ~ 2.83 eV at room temperature, and this value is consistent with the theoretical band gap of LiInSe (~ 2.86 eV). Photoluminescence (PL) spectroscopy was used to analyze the defect concentration. The results indicate that the defect types in the yellow LiInSe single crystal are V and Li; these result from the introduction of excess Li and the suppression of the adverse defects in In and V. These results demonstrate a feasible route for obtaining high-quality yellow LiInSe crystals and promote the application of LiInSe neutron detectors.