Photogalvanic effect of 2D van der Waals heterojunction M2XT2/SiC by first-principles calculations

Abstract

This first-principles study systematically investigates the structural, electronic, and optoelectronic properties of M2XT2/SiC (M = Sc, Y; X = C; T = F, Cl, Br) van der Waals heterojunction. The four examined systems (Sc2CBr2/SiC, Sc2CCl2/SiC, SiC/Y2CF2, and SiC/Y2CCl2) retain their monolayer band characteristics while forming stable heterojunctions with indirect bandgaps. The first three configurations clearly show that the VBM and CBM are confined in SiC and M2XT2, respectively, indicating a type-II band alignment. However, for SiC/Y2CF2, both the VBM and CBM are confined in Y2CF2, indicating a type-I band alignment. Notably, SiC/Y2CCl2 demonstrates exceptional electron mobility (6.99 × 103 cm2 V-1s-1). Charge density difference analysis reveals electron transfer from SiC to MXenes layers, facilitated by a built-in electric field that suppresses carrier recombination. All heterojunctions exhibit enhanced light absorption and reduced bandgaps compared to SiC, with SiC/Y2CF2 showing optimal photoresponse at 3.2 eV photon energy and the highest extinction ratio. These findings highlight the potential of MXenes/SiC heterojunctions for tailored optoelectronic applications.