Stoichiometric effect on the defect states and optical properties of LiInSe2 single crystals

Abstract

Abstract LiInSe2 crystals are promising semiconductor materials for neutron detectors due to the large neutron capture cross-sectional area of the specific isotopes (6Li) 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 LiInSe2 crystals grown by the vertical Bridgman method. The UV‒vis–NIR transmission results indicate that the band gap of the yellow colored Li1.01In1Se2 sample is close to ~ 2.83 eV at room temperature, and this value is consistent with the theoretical band gap of LiInSe2 (~ 2.86 eV). Photoluminescence (PL) spectroscopy was used to analyze the defect concentration. The results indicate that the defect types in the yellow Li1.01In1Se2 single crystal are VSe + and LiIn 2−; these result from the introduction of excess Li and the suppression of the adverse defects in InLi 2+ and VLi −. These results demonstrate a feasible route for obtaining high-quality yellow 6LiInSe2 crystals and promote the application of 6LiInSe2 neutron detectors.

Keywords

• LiInSe2
• Stoichiometric effect
• Point defect
• Band gap