Piezoelectronic Transistor - overview


A new logic device

Introduction – What is a PET?

The PET operates on a novel principle: an electrical input is converted into an acoustic pulse by a piezoelectric element. This, in turn, is used to drive a continuous insulator-to-metal transition in a piezoresistive element, thus switching on the device.

The essentials of the structure consist of a stack of two distinct materials: a piezoelectric (PE) and a piezoresistor (PR) sandwiched between three contacts: the gate, common, and sense. The PE is located between the gate and common contacts, and the PR between the common and sense contacts. Electrically, the gate can be thought of as the device input, and the sense as the output. When an input signal is placed on the gate, a voltage is applied across the PE. Expansion of the PE element results in compression of the adjacent piezoresistive element.

For this to occur, the whole PET stack needs to be vertically clamped within a rigid structure made of a high yield material (HYM), shown above in grey. The piezoresistive material must have a strongly pressure-dependent resistivity, such as found in SmSe, also shown below. For ~4 GPa of pressure, the resistivity changes by almost 7 orders of magnitude, spanning the range from a highly resistive semiconductor down to a metallic regime.

Hence the application of pressure can make the “channel” of the material, between the common and sense contacts, conducting, turning on the device. The net effect is that the input voltage, applied across the capacitor-like input between gate and common, can turn on the path between the common and sense inputs.