Ultra-low resistance Au-free V/Al/Ti/TiN ohmic contacts for AlGaN/GaN HEMTs

Abstract

We report on the electrical and microstructural characterization of an Au-free V/Al/Ti/TiN ohmic contact for AlGaN/GaN heterostructures. Ultra-low contact resistance and specific contact resistivity of Rc < 0.1 Ω mm and ρc < 2.4 × 10−7 Ω cm2 have been achieved with very low RMS surface roughness. This was accomplished at a comparably low annealing temperature of 800 °C and without applying any contact recess, regrowth, or implantation process. High electron mobility transistors were fabricated and a comparison of the electrical performance with state-of-the-art Ti/Al/Ti/TiN and Ti/Al/Ni/Au contacts was made. The contact formation mechanism is discussed on the basis of microstructural features.

Low-field transport properties and scattering mechanisms of degenerate n-GaN by sputtering from a liquid Ga target

“…The recent focus of advanced contact processes is generally driven by CMOS-compatible, Au-free, and/or low-temperature budget ohmic contacts, [8][9][10][11][12] or n-GaN regrowth for highlyscaled AlGaN 5) or novel Al(Sc)N-based HEMTs [13][14][15] with high Al-content. The fabrication of highly n-type doped GaN films was demonstrated via Si implantation, 13,16,17) MBE, [18][19][20][21] MOCVD [22][23][24][25][26] (Si or Ge), pulsed laser deposition (PLD) 27) and reactive, pulsed sputtering (PVD) from a solid Ga target.…”