Negative capacitance overcomes Schottky-gate limits in GaN high-electron-mobility transistors.

Area of Science:

• Materials Science
• Semiconductor Physics
• Device Engineering

Background:

• High-electron-mobility transistors (HEMTs) utilize a two-dimensional electron gas (2DEG) for high performance.
• Schottky gates in AlGaN/GaN HEMTs maximize induced charge and current but suffer from high gate leakage.
• Conventional dielectric layers reduce leakage but also decrease drain current, presenting a performance trade-off.

Purpose of the Study:

• To overcome the limitations of conventional gate dielectrics in HEMTs.
• To achieve simultaneous enhancement of ON current and reduction of leakage current.
• To explore ferroelectric materials as gate dielectrics for advanced semiconductor devices.

Main Methods:

• Fabrication of a ferroic HfO2-ZrO2 bilayer as a gate dielectric.
• Integration of the bilayer into AlGaN/GaN heterostructures for HEMTs.
• Characterization of transistor performance, including ON current and leakage current.

Main Results:

• The HfO2-ZrO2 bilayer significantly increased the ON current compared to conventional Schottky gates.
• A substantial decrease in gate leakage current was observed with the new dielectric.
• This combination of improved ON current and reduced leakage is unprecedented with standard dielectrics.

Conclusions:

• The ferroic HfO2-ZrO2 bilayer offers a novel solution for high-performance HEMTs.
• This approach surpasses the conventional trade-offs associated with Schottky gate designs.
• It opens new avenues for advancing transistors based on 2DEG technology.