CAREER: Nitride FinFET on Silicon for Medium-Voltage Monolithically Integrated Power Electronics

Title: CAREER: Nitride FinFET on Silicon for Medium-Voltage Monolithically Integrated Power Electronics Proposal Number: 2045001 Principal Investigator: Yuhao Zhang Institution: Virginia Polytechnic Institute and State University Nontechnical Abstract

Medium-voltage (600-1700 V) power devices are key for efficient power conversion in electric vehicles, solar farms, power grids, among other applications. They are among the fastest-growing sectors in the $40 billion power semiconductor market. Today’s medium-voltage devices are mainly made of silicon (Si) and silicon carbide (SiC).

Gallium nitride (GaN) has superior physical properties over Si and SiC for power applications. Recently, the vertical GaN power field-effect transistor (FinFET), a new power transistor utilizing sub-micron-meter fin channels, has demonstrated one of the best performances in all medium-voltage transistors. However, all existing vertical GaN FinFETs employ small-diameter and high-cost GaN substrates, which hinders their commercialization.

This CAREER proposal aims at developing a new generation of medium-voltage vertical GaN power FinFETs on low-cost, large-diameter Si substrates with high performance, and fabricating them on the same wafer with the low-voltage lateral GaN FinFETs or tri-gate transistors, hence allowing monolithic integration of the driving circuitry and medium-voltage power devices for the first time. This project, if successful, will enable an unprecedented advancement in the performance, frequency, efficiency, and form factor of the medium-voltage power electronic systems.

This project provides opportunities for student education and outreach: (a) establishing an integrated undergraduate research program tackling interdisciplinary problems in the fields of materials, devices, and power electronics; (b) mentoring the participating students with the industrial collaborators and promoting the student interactions with the power semiconductor industries; (c) contributing to the pre-college summer camps and providing summer research opportunities to K-12 students and teachers in microelectronics. The program will actively engage students from a broad range of groups in microelectronics research and education.

Technical Abstract

The overarching objective of this project is to build a monolithic “full GaN FinFET” platform on Si substrates, which shares common processing technologies and device building blocks, where the high-voltage, vertical GaN FinFET is employed for power processing and the low-voltage, lateral GaN FinFETs/trigate FETs are used for information processing. The interdisciplinary nature of this project offers significant intellectual merits in materials, devices, processing technologies, and power modules: (a) New characterization methods will be established to map the leakage current in GaN-on-Si with spatial resolutions down to the nanometers and characterize the trap-mediated breakdown voltage with temporal resolutions down to the nanoseconds. (b) Innovative function structures will be explored to overcome the insulating and highly-defective buffer layers in GaN-on-Si structure and enable superior electrical, thermal, and mechanical performances in fully-vertical GaN-on-Si power FinFETs. (c) Innovative epitaxial structure and fabrication processes will be established to enable the monolithic integration of medium-voltage vertical FinFETs and lateral digital FinFETs/tri-gate-FETs. (d) Advanced models and simulations will be explored to link the microscopic material non-idealities and circuit dynamics to device designs and optimizations, which has been a long knowledge gap in nitride devices and materials.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.