Designing piezoresistive materials from first-principles: Dopant effects on 3C-SiC

Abstract

The piezoresistive effect is widely exploited in Si-based sensor technology, in part due to Si’s high gauge factor. However, for harsh environments, wider bandgap materials, such as SiC, are desirable. Despite the quest to improve its piezoresistance, SiC’s gauge factor remains low, although recent experiments hint towards doping as a viable strategy. To search for the best dopant, we developed a computational framework, based on density functional theory (DFT) and Boltzmann Transport calculations, to compute the piezoresistive properties of materials and apply it to predict the gauge factor and piezoresistive coefficient of doped-SiC. Under rigid band approximation, predicted gauge factor of lightly-doped SiC (1.0 × 1018 cm−3) agrees reasonably with experimental values. For moderately doped SiC, we explicitly substitute the doping element into a 64-atom supercell of SiC and compute the piezoresistive properties. We discover that effective dopants consist of elements that could exist in +4 oxidation states. Among them, Ru leads to a 4-fold increase in gauge factor, while Mo and Pt are peculiarly suitable for high-temperature use, where their gauge factors increase with temperature. From bandstructure analysis, we elucidate that promising dopants, under strain, impact resistivity through changes in band positions and curvature. We also discuss the formability of the doped-SiC systems. Furthermore, we demonstrate correlations among piezoresistive properties and their dependence on crystallographic orientations and temperature. The framework serves as a starting point for rational computational design of piezoresistive materials.