Mass Transport Regrowth of GaN for Ohmic Contacts to AlGaN/GaN

Abstract

A novel selective area mass transport regrowth technique for n + -GaN, requiring no Ga or Si precursor, was developed for low resistivity contact formation to AlGaN/GaN HEMTs. Masked samples were reactive ion etched followed by a short anneal in NH 3 and H 2 at 1050-1080 °C. During annealing mass transport occurred from large open areas to mask edges and narrow mask openings. Autodoping from the SiO 2 mask provided n-type doping. After depositing Ti/Al/Ni/Au contacts, the contact resistance was measured to ∼0.3 Ω mm, showing a weak dependence on the annealing temperature. Devices with regrown contacts were fabricated, achieving a power density of 4.8 W/mm at 8 GHz. The technique provides a low-cost regrowth process, with applications in particular for high Al composition AlGaN/GaN devices.