Understanding The Breakdown Characteristics Of Lateral GaN-Based HEMTs

by Michael A. Briere, ACOO Enterprises under contract to International Rectifier, El Segundo, Calif, How2Power Today, Sep 16 2013

Focus:
For lateral GaN-based HEMTs formed on silicon substrates, it has been suggested that the breakdown of these devices through catastrophic, non-recoverable, dielectric failure is both unexpected and undesirable. However, this behavior is neither unexpected nor essentially undesirable. Lacking a spatially resolved PN junction, lateral GaN-based HEMTs do not exhibit recoverable breakdown behavior and have no avalanche capability. Their primary breakdown mechanism is dielectric breakdown of the overlying insulating layers in the device. In that regard, they resemble ceramic capacitors more so than silicon power semiconductor devices. This major difference in breakdown behavior affects how the new GaN-based devices should be designed, rated, and specified in power electronics applications. In addition, there are secondary breakdown mechanisms such as leakage that will influence device design and ratings. All of these issues will be discussed in this article with an eye toward giving the power system designer a clearer understanding of how to compare the new lateral GaN-based HEMTs with existing silicon and silicon carbide-based devices.

What you’ll learn:

• How to understand the breakdown mechanisms of lateral GaN HEMT power devices and how they differ from conventional silicon- and silicon carbide-based power devices
• How to understand how dielectric breakdown and leakage determine maximum voltage ratings for GaN HEMT power devices

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