A Demonstration of Nitrogen Polar Gallium Nitride Current Aperture Vertical Electron Transistor

We report the first demonstration of Nitrogen polar (N-polar) GaN current aperture vertical electron transistor with a blocking electric field over 2.9 MV/cm. The devices were grown by metalorganic chemical vapor deposition on a c-plane sapphire substrate. The fabrication involved a maskless planar regrowth of a very thin-AlN layer above the current blocking layer, which induced a two-dimensional electron gas (2DEG) in the channel, and also prevented the out-diffusion of activated Mg ions into the GaN channel layer. The alloyed source and drain ohmic contacts on the regrown n ⁺ -GaN layer offered the low-contact resistance of 0.18 mQ · cm ² (0.22 Ω · mm). The device displayeda maximum drain current of 1.68 kA/cm ² with a low RON,SP of 2.48 mQ · cm ² . With just about 200 nm drift layer, a three-terminal breakdown voltage of 58 V was achieved. The output characteristics were free of dispersion under pulsed measurements with 80 μs and 500 ns pulse widths. The N-polar current aperture vertical electron transistors show fundamentally significant advantages in favor of using Mg ²⁺ -implanted GaN as current blocking layers compared with Ga-polar counterparts.