Tined gate to control threshold voltage in a device formed of materials having piezoelectric properties

Abstract

Roughly described, a field effect transistor has a first piezoelectric layer supporting a channel, a second piezoelectric layer over the first piezoelectric layer, a dielectric layer having a plurality of dielectric segments separated by a plurality of gaps, the dielectric layer over the second piezoelectric layer, and a gate having a main body and a plurality of tines. The main body of the gate covers at least one dielectric segment of the plurality of dielectric segments and at least two gaps of the plurality of gaps. The plurality of tines have proximal ends connected to the main body of the gate, middle portions projecting through the plurality of gaps, and distal ends separated from the first piezoelectric layer by at least the second piezoelectric layer. The dielectric layer exerts stress, creating a piezoelectric charge in the first piezoelectric layer, changing the threshold voltage of the transistor.

Description

Background technique [0001] The technology of the present invention involves heterojunction field effect transistors (HFETs) including high electron mobility transistors (HEMTs) or metal insulator semiconductor HFETs (MISHFETs) or dual-channel HFET / HEMT / MISHFET or dual-channel HFET / HEMT / MISHFET , or thin body (SOI, FinFET, Tri-Gate, Gate All Around, etc.) HFET / HEMT / MISHFET), which can be used as switching devices, for example. Such devices are typically formed from III-V semiconductors and achieve very high mobility by having an undoped channel region. In a conventional HFET, the device is described as "normally on," meaning that the threshold voltage (also known as the pinch-off voltage) is zero or negative, and the channel conducts current with little bias applied between the source and gate. with or without bias. For power electronics applications, normally-off devices are more preferred for reasons of safety, energy conversion and circuit design. For example, a normally...

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Problems solved by technology

Like other methods, additional deposition, etch, and cleaning steps are required, adding to device complexity and cost

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