Gallium Nitride Power Devices Using Nanosheet-Typed Channel Layers

The field of radio-frequency (RF) electronics, particularly involving gallium nitride (GaN) devices, is critical for advanced applications such as radar systems and next-generation 5G communications. A continuing pressing need in this area is for advancements to achieve high power densities essential for developing more efficient, compact, and powerful phased arrays fundamental to modern communication and sensing technologies requiring high performance. Current approaches utilizing conventional GaN field-effect transistors (FETs) encounter substantial limitations, typically achieving power densities restricted to approximately 7 to 10 W/mm. These performance ceilings stem from several critical, interconnected issues. A primary challenge is the inherently high thermal junction-to-packaging resistance, often around 30 K mm/W, which severely impedes efficient heat dissipation from the active device area. Furthermore, epilayer defects within the GaN material contribute significantly to performance degradation, and excessive gate-leakage current remains a persistent problem, hindering overall device efficiency, reliability, and power-handling capabilities.

Technology Description

This wide-band gap transistor device incorporates two spaced, undoped gallium nitride (GaN) fins extending orthogonally from a substrate. A p-type GaN dielectric layer is conformally deposited, encapsulating one or more n-type GaN nanosheet heterostructures that serve as the channel between the fins. Source and drain contacts are placed over these nanosheet channels, with a gate electrode atop a p++ GaN layer controlling current. This architecture enables normally-off operation by forming a lateral p-n junction that depletes the channel at zero gate bias, reducing leakage. Stacking multiple nanosheets in parallel increases drain current and power density. The device can also be lifted off and bonded to diamond substrates for enhanced thermal dissipation.

This technology is differentiated by its ability to achieve significantly higher power densities for RF applications, overcoming limitations of conventional GaN field-effect transistors. It reduces gate leakage current by 30 to 70% and increases drain current by utilizing multiple nanosheet stacks. Crucially, it achieves power densities comparable to much larger planar devices, requiring a device area over 400 times smaller. Enhanced thermal management is provided through double-sided bonding to diamond substrates. The normally-off operation further contributes to reduced leakage, making it highly suitable for high-frequency, high-power millimeter-wave RF applications with a reduced footprint.