New Developments in Gallium Nitride and the Impact on Power Electronics

Abstract

Wide bandgap III-nitride semiconductor materials possess superior material properties as compared to silicon, GaAs and other III-V compound materials. Recent achievements in gallium nitride (GaN) technology for optoelectronics have resulted in ultra-bright blue light emitting diodes and lasers, ultraviolet emitters, and solar-blind optical detectors. In the electronic area, drastic improvement of microwave device performance has been achieved, yielding record high power densities of 20-30 W/mm. Novel applications of these materials in high-power electronics for switching, energy conversion and control are just emerging. This paper provides an overview of the state-of-the-art III-nitride wide bandgap technologies and it explores power electronic applications while illustrating the enormous potential that GaN based devices have for overcoming the major challenges of power electronics in the 21st century. The paper discusses the unique material and device properties of GaN-based semiconductors that make them promising for high-power, high-temperature applications. These include high electron mobility and saturation velocity, high sheet carrier concentration at heterojunction interfaces, high breakdown voltages, and low thermal impedance (when grown over SiC or bulk AIN substrates). The chemical inertness and radiation hardness of nitrides are other key properties. As applied to power electronics, the Ill-Nitride technology allows for high-power switching with sub-microsecond and nano-second switching times. The paper will present the innovations that further improve the performance of high-power DC-DC converters, switches and other building blocks. These include novel insulated gate HFET design that significantly expands the allowable input voltage amplitude, further increases the device peak currents, and most importantly, tremendously improves the large-signal stability and reliability. Insulated gate switching devices have been shown to operate at up to 300 degC with no noticeable parameter degradation. Novel monolithic integrated circuits of high-power switches and DC-DC converters and their performance parameters will be presented. The paper also discusses the major challenges associated with modern GaN technology and work in progress to overcome them