A pressure-sensitive oscillator for neuromorphic applications

A post-CMOS compatible pressure sensor and associated readout electronic circuits are presented, which in combination yield a pressure sensitive artificial neuron with spike-frequency coded output. The transducers consist of a custom made metal-oxide-semiconductor field effect transistor, comprising a piezoelectric aluminum scandium nitride layer inside the gate stack (piezo-FET). They can operate in either a diode configuration or as current mirror pairs. The operating regime is CMOS compatible. The pressure dependent output current feeds a CMOS ring oscillator, varying its output frequency. The neuron is designed for off-chip coupling into a neural spiking network. Measured results are shown for the piezo-FET, readout setup, and oscillator, confirming the capability of encoding the mechanical quantity into a series of frequency-modulated spikes.