Computational study of self-trapped hole in KH2PO4–Si crystal

Abstract

We use the DFT + U approach to investigate the properties of self-trapped holes (STHs) in silicon (Si)-doped potassium dihydrogen phosphate (KH2PO4) crystal. The calculated electronic structure and spin density indicate that the hole is trapped by an oxygen around the Si atom. The STH is stable under room temperature, as the self-trapped energy is as high as 0.50 eV. The optical properties of the localized and delocalized holes of KH2PO4-Si crystals are also calculated, and the results show that the emission energy of the STH [3.62 eV (343 nm)] is consistent with the experimental photoluminescence of KH2PO4 (342 nm), and the absorption peaks of the STH [3.58 eV (346 nm) and 5.56 eV (223 nm)] are located in the ultraviolet (UV) region, which indicates a close connection between the STH and the absorption band in the UV region. The absorption peak of the delocalized hole [3.44 eV (360 nm)] is consistent with the experimental absorption band (360 nm). Therefore, Si impurities result in UV absorption and a sharp decline of damage threshold in KH2PO4.