Gate stack for normally-off compound semiconductor transistor

Abstract

The embodiment of the invention discloses a gate stack for normally-off compound semiconductor transistor. The normally-off compound semiconductor transistor includes a heterostructure body and a gate stack on the heterostructure body. The heterostructure body includes a source, a drain spaced apart from the source, and a channel for connecting the source and the drain. The channel includes a first two-dimensional charge carrier gas of a first polarity arising in the heterostructure body due to piezoelectric effects. The gate stack controls the channel in a region of the heterostructure body under the gate stack. The gate stack includes at least one III-nitride material which gives rise to a second two-dimensional charge carrier gas of a second polarity opposite the first polarity in the gate stack or in the heterostructure body under the gate stack due to piezoelectric effects. The second two-dimensional charge carrier gas counter-balances polarization charges in the first two-dimensional charge carrier gas so that the channel is disrupted under the gate stack.

Description

technical field [0001] This application relates to compound semiconductor transistors, and more particularly to normally-off III-nitride-based transistors. Background technique [0002] Conventional HEMTs (High Electron Mobility Transistors) are typically fabricated in GaN technology and are often characterized by negative threshold voltages. That is, current flows between the source and drain terminals of the device even when no voltage is applied to the gate electrode to turn on the transistor. In fact, in GaN technology, a thin channel (inversion layer) is created automatically, without applying any voltage to the gate electrode, via strain and polarization effects between the source and drain terminals. As such, the device is often referred to as normally open. [0003] The normally-on characteristic of HEMTs is an intrinsic property of GaN technology and limits the range of applications of GaN technology to those applications where a power supply can be used to genera...

AI Technical Summary

Problems solved by technology

[0005] However, unlike conventional silicon technologies, the doping of large bandgap materials such as GaN is not trivial

In practice, the fabrication of thin p-type doped GaN layers requires very complex processing

Moreover, threshold voltage instability can arise due to non-uniform doping of the GaN layer, and especially due to surface accumulation of p-type dopant elements at the exposed GaN surface

Furthermore, the maximum gate voltage that can be tolerated by the device is limited by the presence of a pn junction below the gate electrode

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