Effect of Ga substitution for In in LiInSe2 crystals on carrier transport behaviors and alpha particles detection

Abstract

Due to high density of 6Li isotope and the ability to respond to ionizing radiation through direct charge carrier transport, Li-containing chalcogenides are expected to be the replacement of 3He-tube or neutron reactive material coated semiconductor films for thermal neutron detection. However, the neutron detection efficiency of 6LiInSe2 is limited to 82% ascribed to that 115In isotope captures neutrons and generates gamma rays, which deteriorated the neutron response. Neutron detection efficiency could be improved by gallium substitution since its low neutron capture cross-section. In this work, the electron and hole mobility (μ) of LiIn1−xGaxSe2(x = 0, 0.25, 0.5, 0.75, 1) were studied by first-principles density functional theory (DFT) calculation, which demonstrated the electron mobility (μ e) of LiIn0.5Ga0.5Se2 is close to that of LiInSe2 while the hole mobility (μ h) is much improved. To further certify, both LiIn0.5Ga0.5Se2 and LiInSe2 crystals were grown under similar condition by vertical Bridgman method, exhibited comparable bandgap and bulk resistivity at room temperature. The charge transport behaviors were evaluated under 241[email protected] alpha particles. The full energy peak is clearly resolved in the pulse height spectra. The electron and hole mobility-lifetime products of LiIn0.5Ga0.5Se2 are 1.5×10−5 cm2/V and 6.9×10−5 cm2/V, respectively. The resulting μ e of LiIn0.5Ga0.5Se2 and LiInSe2 crystals are 270 cm2V−1s−1 and 180 cm2V−1s−1, respectively, fitted by time of flight (TOF) technique. In addition, the μ h of LiIn0.5Ga0.5Se2 is obtained with the value of 110 cm2V−1s−1, but the hole response is too weak to be resolved for LiInSe2.