Pulsed sputtering selective epitaxial formation of highly degenerate n-type GaN ohmic contacts for GaN HEMT applications

This study describes the selective formation process of highly degenerate n-type GaN (d-GaN) ohmic contacts for the source and drain regions of GaNHEMTs using pulsed sputtering deposition (PSD). The selective formation process using SiO2 masks and PSD epitaxial growth enabled the uniform formation of d-GaN in micron-meter size. Transmission-line-method measurements demonstrated that the contact resistance of GaN HEMTs with d-GaN regrowth contacts was remarkably low at 0.28 Ωmm, leading to reasonable DC output characteristics. These findings suggest that PSD epitaxial regrowth of d-GaN is a promising approach for the high-throughput formation of low-resistivity ohmic contacts on large-area GaN HEMT wafers.