Summary: Researchers in the UCLA Department of Electrical and Computer Engineering have developed a new, high-performance transistor for high-frequency and high-power systems.
Background: Gallium nitride (GaN) high electron mobility transistors (HEMTs) are critical for high-frequency and high-power electrical applications due to their superior material properties, including their high electron mobility, electron saturation velocity, and breakdown field. Of these, N-polar GaN HEMTs are of particular utility over G-polar GaN HEMTs due to their improved charge confinement and enhanced charge density enabled by a thick GaN cap layer. However, despite the advantages of N-polar GaN HEMTs, manufacturing challenges remain. Industry-standard manufacturing of N-polar GaN HEMTs uses silicon nitride (SiN) dielectric gates, which must be deposited at high temperatures, limiting process flow, and a moderate dielectric constant, which hinders performance. To broaden industry adoption and widespread application of N-polar GaN HEMTs, there is an unmet need to overcome these fundamental limitations.
Innovation: To address these limitations, inventors led by Professor Elaheh Ahmadi have developed atomic layer deposition (ALD) hafnium-based (HfSiO) gate dielectrics in N-polar GaN HEMTs. ALD is a widely used and accessible tool used throughout global semiconductor manufacturing. The low deposition temperatures of ALD eliminate traditional process limitations, allowing metal and even photoresist on samples prior to deposition. This enables new processes and earlier quality control checkpoints. The researchers have shown that their HfSiO gates outperformed SiN gates with superior voltage performance, reduced dispersion, and enhanced power output at higher voltages. These results show the significant potential of HfSiO with N-polar GaN HEMTs for broad electronic applications.
Potential Applications: • Wireless communications • Electric vehicles • Power delivery systems • Microwave/RF • Military/defense
Advantages: • High power delivery • High frequency switching • Scalable manufacturing • Upstream quality control
Development-To-Date: Researchers have manufactured and validated HfSiO N-polar GaN HEMTs for improved performance.
Related Papers:
O. Odabasi, S. Mohanty, K. Khan and E. Ahmadi, "N-Polar GaN Deep Recess HEMT With Atomic Layer Deposition HfO2 as Gate Insulator," in IEEE Transactions on Electron Devices, vol. 70, no. 9, pp. 4572-4577, Sept. 2023, doi: 10.1109/TED.2023.3295352.
HfO2 as gate insulator on N-polar GaN–AlGaN heterostructures
Reference: UCLA Case No. 2024-268
Lead Inventor: Associate Professor Elaheh Ahmadi, UCLA Department of Electrical and Computer Engineering