A pressure sensitive silicon field effect transistor comprising a buffer-free piezoelectric Al0.72Sc0.28N layer

Abstract

Modified metal-insulator-semiconductor field effect transistors comprising piezoelectric materials are considered attractive devices for pressure sensing. In this work, we present a n-channel modified metal-insulator-semiconductor field effect transistor which consists of a 100 nm thick piezoelectric Al_0.72Sc_0.28N layer in the gate stack. The functional Al_0.72Sc_0.28N layer was deposited by sputtering directly, i.e. buffer-free, on the Si-channel. The transistors are located at the ends of Si cantilevers. Under a defined cantilever bending, transistors exhibited a sensitivity (∆I_DS /∆F) up to 30 (nA/N).

The structure of the piezoelectric Al_0.72Sc_0.28N layer, as deposited on Si, was investigated by wide-range reciprocal space mapping and pole figures. Cross-sections of the gate stack were analysed using Transmission Electron Microscopy and Electron Energy Loss Spectroscopy, which revealed no evidence of a residual interfacial layer.