Nonalloyed ohmic contact of AlGaN/GaN HEMTs by selective area growth of single-crystal n ⁺-GaN using plasma assisted molecular beam epitaxy

Selective area growth (SAG) based on plasma assisted molecular beam epitaxy (PAMBE) was demonstrated to be effective to achieve low contact resistance for nonalloyed ohmic metals. An AlGaN/GaN high-electron mobility transistor (HEMT) using SAG by PAMBE with nonalloyed ohmic metals and recessed drain/source structure exhibited a low specific contact resistance of 3.7 × 10 ^-5 cm ², high-peak drain current of 604 mA/mm, and small gate leakage current of 3.4 μA. These results demonstrate that SAG by PAMBE produces nonalloyed HEMT with comparable or more favorable electric performance versus conventional alloyed counterpart while avoiding problems of the latter resulting from high-temperature annealing.