Surface acoustic wave rfid sensor for hemodynamic wearables

A surface acoustic wave (SAW) radio-frequency identification (RFID) sensor chip comprising:

• a piezoelectric substrate, said substrate comprising a piezoelectric layer and a multilayer heterojunction structure, said structure being made of III-V single-crystalline or polycrystalline semiconductor layers, deposited on said piezoelectric layer and comprising at least one buffer layer and at least one barrier layer, said layers being stacked alternately;
• at least one pair of metal interdigitated transducers (IDT) mounted on said piezoelectric substrate, for receiving a radio frequency (RF) input signal, transducing said input signal into a surface acoustic wave (SAW), propagating said surface acoustic wave along a surface of said piezoelectric substrate and transducing said propagated surface acoustic wave into an output RF signal;
• at least one normally-on or normally-off two-dimensional electron gas (2DEG) or two-dimensional hole gas (2DHG) structure grown or recessed in said multilayer heterojunction structure on said piezoelectric substrate to form a normally-on or normally-off 2DEG or 2DHG conducting channel in said multilayer heterojunction structure at the interface between said buffer layer and said barrier layer;
• at least one pseudo-conducting 2DEG or 2DHG structure deposited grown or recessed in said multilayer heterojunction structure on said piezoelectric substrate to form a pseudo-conducting 2DEG or 2DHG channel in said multilayer heterojunction structure at the interface between said buffer layer and said barrier layer;
• and
• electrical metallizations capacitively-coupled to said IDTs, to said normally-on or normally-off 2DEG or 2DHG structures and to said pseudo-conducting 2DEG or 2DHG structures for inducing displacement currents, thereby creating non-ohmic source and drain contacts, for connecting said sensor chip to an electric circuit.