Heteroepitaxy of Hf0.5Zr0.5O2 ferroelectric gate layer on AlGaN/GaN towards normally-off HEMTs

Ferroelectric gate High Electron Mobility Transistors (HEMTs) stands out as a promising route for normally-off HEMTs. HEMTs based on perovskite ferroelectrics, however, suffer from low threshold voltage, electrical instability, and CMOS process incompatibility. In this work, fluorite Hf0.5Zr0.5O2 (HZO) was designed to serve as ferroelectric gate layer for normally-off HEMTs, and HZO/MgO/AlGaN/GaN/Si ferroelectric-semiconductor heterostructure was constructed by pulsed laser deposition. The epitaxial relationship was revealed to be [112](11 1) HZO//[112](1 1 1) MgO//[1010](0002) GaN, and corresponding domain matching mechanism was determined as 6aMgO = 5aHZO. Strong coupling effect between ferroelectric polarization of HZO and twodimensional electron gas (2DEG) at AlGaN/GaN interface was confirmed by continuous modulation of threshold voltage from -3.8 V to +3.2 V through regulating polarization state of 15 nm HZO. Moreover, relatively weak depolarization effect of HZO on AlGaN/GaN was observed, which was crucial for device electrical stability. In addition, ultrahigh threshold voltage of +5.5 V was detected in designed heterostructure with 50 nm HZO. Our work demonstrates that epitaxial HZO ferroelectric gate layer on AlGaN/GaN possesses high threshold voltage, good device electrical stability and great semiconductor process compatibility, emerging as great potential for developing and miniaturizing high-performance normally-off HEMTs.

Automated summary

In this work, Hf0.5Zr0.5O2 (HZO) fluorite was designed as a ferroelectric gate layer for normally-off HEMTs, and an HZO/MgO/AlGaN/GaN/Si ferroelectric-semiconductor heterostructure was constructed. The heterostructure exhibited high threshold voltage, good device electrical stability, and great semiconductor process compatibility on AlGaN/GaN.