Design-dependent gauge factors of highly doped n-type 4H-SiC piezoresistors

This paper presents the experimentally obtained gauge factor (GF) of 4H-SiC piezoresistors, fabricated out of the n-type epitaxial layer and characterized on millimeter-size SiC cantilever beams at room temperature. It was found that the GF is dependent on the piezoresistor's length and width. Piezoresistors narrower than approximately 30 mu m showed a width-dependent GF. The highest GF of 20.8 was obtained with a single element piezoresistor in transverse orientation. In longitudinal orientation, the highest GF was -10, which was obtained with a clustered piezoresistor with plural identical elements. Essential factors to consider for the design of optimum 4H-SiC piezoresistors for a Wheatstone bridge configuration are presented.