Nonalloyed Ti/Al Ohmic contacts to n‐type GaN using high‐temperature premetallization anneal

On Si‐implanted n‐type GaN, a nonalloyed Ti/Al metallization has been found to form an Ohmic contact that has a specific contact resistance as low as 1.0×10⁻⁵ Ω cm². The Ohmic character is believed to be caused by the 1120 °C implant activation anneal which generates nitrogen vacancies that leave the surface heavily n type. This theory is indirectly confirmed on unimplanted n‐type GaN by comparing the r_c of nonalloyed Ti/Al on unannealed GaN with that of nonalloyed Ti/Al on 1120 °C annealed GaN. The former has rectifying electrical characteristics, while the latter forms an Ohmic contact with an r_c=1.3×10⁻³ Ω cm².