Development of Fabrication Techniques for N-Polar GaN HEMTs
Abstract
Nitrogen-polar (N-polar) gallium nitride (GaN) high electron mobility transistors with the deep recess structure have recently demonstrated exceptional large-signal performance at millimeterwave frequencies. In particular, within W-band, at 94 GHz, up to 8 W/mm of output power density has been obtained which represents a 4x improvement over traditional gallium-polar (Gapolar)devices at similar frequencies while maintaining a high power-added efficiency in excess of 27%. These observed performance benefits of N-polar GaN arise from device design advantages associated with the inverted polarization-induced electric fields relative to a Ga-polar GaN-based transistor. For millimeter-wave devices, the addition of a GaN cap layer in the device access regions provides the dual advantage of increased access region conductivity with control over dispersion. In addition to the inverted polarization electric fields which provides advantages in device design, the N-polar orientation also offers a second difference in characteristics in that the N-polar surface is more chemically reactive than Ga-polar GaN. This difference between the two orientations creates the possibility for different device fabrication approaches for N-polar GaN relative to gallium polar GaN. To date, for the fabrication of these N-polar transistors, techniques and processes which were initially developed for Ga-polar devices have generally been applied to N-polar device fabrication with minimal optimization for the N-polar orientation. In this work we will leverage the different properties of the N-polar surface to develop improved device fabrication techniques and processes which are unique to N-polar GaN.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 17, 2020
- Source ID
- N000142012166
Entities
People
- Umesh Mishra
Organizations
- Office of Naval Research
- United States Navy
- University of California, Santa Barbara