Gallium-nitride-based heterojunction field effect transistor with combined gate dielectric layer

Abstract

The invention discloses a gallium-nitride-based heterojunction field effect transistor with a combined gate dielectric layer. The gallium-nitride-based heterojunction field effect transistor sequentially and mainly comprises a substrate, a gallium nitride buffering layer, a gallium nitride channel layer, an aluminum gallium nitrogen barrier layer and the combined gate dielectric layer from bottom to top. A source, a drain and a gate are formed on the barrier layer, wherein the source and the drain are in ohmic contact with the barrier layer, and the gate is in schottky contact with the barrier layer. The combined gate dielectric layer is composed of gate dielectric layer bodies different in dielectric constant. In this way, an electric field peak value is formed on the gate dielectric layer interface of the channel layer, a peak value of the electron drifting speed exists at the portion of the electric field peak value, and the drifting speed of electrons in a whole channel is accordingly increased; meanwhile, due to the gate dielectric layer body with the low dielectric constant, the gate capacitance is reduced, and the frequency characteristic of a device is improved.

Description

technical field [0001] The invention relates to the field of semiconductor devices, in particular to a gallium nitride-based heterojunction field effect transistor with a composite gate dielectric layer. Background technique [0002] Gallium nitride (GaN) based heterojunction field effect transistor has excellent characteristics such as large band gap, high critical breakdown electric field, high electron saturation velocity, good thermal conductivity, radiation resistance and good chemical stability. (GaN) materials can form two-dimensional electron gas heterojunction channels with high concentration and high mobility with materials such as aluminum gallium nitride (AlGaN), so they are especially suitable for high-voltage, high-power and high-temperature applications, and are the most suitable for power electronics applications. One of the most promising transistors. [0003] figure 1 It is a schematic diagram of a traditional GaN MIS-HFET structure based on the prior art...

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Problems solved by technology

Shortening the gate length has high requirements on the process. At the same time, with the shortening of the gate length, a serious short channel effect will occur, resulting in an increase in the subthreshold current of the device, an unsaturated output current, a decrease in the maximum DC transconductance, and a shift in the threshold voltage. Phenomena such as the decrease of the product of the frequency grid length and the like ["Short-Channel Effect Limitations on High-Frequency Operation of AlGaN / GaN HEMTs for T-Gate Devices", IEEE Trans. Electron Devices, vol.54, no.10, pp.2589- 2597,Oct.2007.], which has adverse effects on the electrical properties of the device

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