A low-resistance, thermally stable Ohmic contact to n-GaSb

Ohmic contacts to gallium antimonide have been studied in recent years in an attempt to develop a low-resistance, thermally stable metallization. We present a study of Pd3 In7 XAu (X=Pt, W, W Si2, or WSiN) contacts that utilize Pd and In to obtain a low contact resistance, and a diffusion barrier (X) to ensure thermal stability of the contact beneath the gold cap. Contacts utilizing WSiN as the diffusion barrier exhibit specific contact resistance values comparable to the best previously reported, but with greatly improved thermal stability and shallow reaction morphology. The Pd3 In7 WSiNAu contact provides a specific contact resistance of 1.8× 10-6 Ω cm2 after annealing at 325 °C for 1 min or 350 °C for 30 s (n≃2× 1018 cm-3). Field emission is identified as the mechanism for current transport in these contacts. The reaction depth of the contact remains less than 30 nm after at least 400 h at 250 °C in an evacuated ampoule, along with an increase in specific contact resistance to 7× 10-6 Ω cm2.