Novel Structures for Scalable Vertical Gallium Nitride Power Devices

Abstract

Solid state electronic devices have been the backbone of modern power systems for decades. However, as we enter an era fuelled by renewable energy and defined by pervasive electrification, novel power devices must be developed to address the increasingly stringent demands for high power density and efficiency. In this thesis, the theory and fabrication of several new gallium nitride (GaN) power devices will be developed to push beyond current device limitations.

A key advancement surrounds the acknowledgment that vertical GaN power devices are fundamentally three-dimensional. Fabrication of these devices does not readily benefit from the decades of expertise gained in planar processing within the silicon industry. Instead, we will present how a new approach to creating vertical fin-based devices will enable self-aligned fabrication of vertical GaN finFETs and related devices.

Within this work, we also explore the scalability of vertical GaN finFETs. Working with 8-inch GaN substrates, we demonstrate that vertical finFETs can be fabricated using a fully CMOS compatible process flow. This enables a scalable pathway to the widespread adoption of GaN by leveraging existing manufacturing capabilities.

As a final look towards the future of GaN devices, we explore methods to surpassing the one-dimensional, unipolar limit of GaN through devices known as superjunction. The theory that has been highly successful for Si devices is applied to GaN, and a new framework for designing devices is presented. Using our approach to creating vertical fin-based devices, we are able to fabricate record high aspect-ratio demonstrations of a new class of fin diodes that reveal a promising path towards the next generation of GaN power devices.