原位生长SiNx在AlN/GaN高电子迁移率晶体管欧姆接触形成中的作用

This study investigates the formation and optimization of ohmic contacts on in-situ grown Silicon Nitride (SiN x ) on AlN/GaN high electron mobility transistors (HEMTs) for high-frequency applications. Using the standard Ti/Al/Ni/Au metal scheme, the achieved contact resistance (R C ) is 0.14 Ω·mm, with a sheet resistance (R SH ) of 629 Ω/□ and specific contact resistance of 1.2 × 10 −6 Ω·cm 2 . The high-temperature annealing of the contact induces the interfacial reaction between the Ti and underlying SiN x layer, leading to titanium silicide (Ti x Si y ) complexes and titanium nitride (TiN). The annealing of the contact was done using rapid thermal process (RTP) in N 2 ambient, and 800 °C for 60 s was found to give the best contact resistance. The same ohmic contact is used to realize the HEMT device with a gate length (L g ) of 200 nm and a source-drain spacing (L sd ) of 4 µm, achieving a maximum drain current (I D ) of 1.02A/mm at V ds = 1 V with on-resistance (R ON ) 4.2 Ω·mm and a peak transconductance (g max ) of 340 mS/mm.