Vertical GaN Schottky Barrier Diode With Record Low Contact Resistivity on N-Polarity Using Ultrathin ITO Interfacial Layer

In this article, an ohmic contact structure based on indium tin oxide (ITO)/Ti/Al/Ni/Au is explored for high-performance GaN-on-GaN Schottky barrier diode (SBD) for the first time. Owing to the ultrathin ITO interfacial layer, the Fermi-level pinning (FLP) effect in metal-semiconductor interface could be mitigated, thus the specific contact resistivity ( $\rho _{c}{)}$ on N-polarity was reduced from $3.32\times 10^{-{3}}$ to $7.36\times 10^{-{5}}\,\,\Omega $ cm2, and the specific ON-resistance ( ${R}_{\text {ON}}{)}$ of the device was reduced from 3.14 to 1.17 $\text{m}\Omega $ cm2 under the same testing condition. With the Helium ion implantation technology, a high breakdown voltage ( ${V}_{\text {BR}}{)}$ of 1100 V, low turn-on voltage ${V}_{\text {ON}}$ of 0.63 V, and a high figure of merit ( ${V}_{\text {BR}}^{{2}}/{R}_{\text {ON}}{)}$ of 1.04 GW/cm2 were achieved in this work. The vertical GaN SBD with ITO interfacial layer fabricated in this work achieved the lowest $\rho _{c}$ in the reported GaN-on-GaN SBDs with an indicated anode size.