Fabrication of a $\hbox{TiN}_{x}/\hbox{Ni/Au}$ Contact on ZnO Films With High Thermal Stability and Low Resistance

A novel contact structure comprising of TiN
_1.22
/Ni/Au has been deposited on Ga-doped and In-doped zinc oxide (ZnO) epilayer grown on a yttria-stabilized ZrO
₂
substrate. It is found that the contact resistivity ρ
_c
is around 10
^-7
Ω cm
²
for heavily doped ZnO, whereas a ρ
_c
value of 10
^-5
Ω cm
²
is achieved for ZnO with light doping concentration. Attributed to the barrier effect of TiN
_1.22
intermediate layers, thermal annealing does not change the contact resistivity, but it is affected significantly by different surface treatments (atomic oxygen or nitrogen). For atomic oxygen-treated ZnO surface, the carrier density is increased, which leads to lower contact resistivity. It is shown that the contact structure of TiN
_1.22
/Ni/Au with TiN
_1.22
as the intermediate layer can provide a high-quality ohmic contact with low ρ
_c
and good thermal stability.