A Vertical-Structured Ni/GaN Schottky Barrier Diode Using Electroplating Nickel Substrate

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In this work, a vertical-structured Ni/$u$-GaN (2 μm)/$n$-GaN (1.5 μm) Schottky barrier diodes (SBDs) employing an electroplating nickel substrate and laser lift-off processes is proposed and experimental results are reported. A metal system comprising a Ti/Al/Ti/Au mutilayer structure was used to form ohmic contact to $n$-GaN. A specific contact resistance as low as $6.64\times 10^{-5}$ $\Omega$$\cdot$cm2 has been obtained after sample thermal annealing in Ar ambient at 800 °C for 30 s. A KOH etching to the $u$-GaN epilayer after the removal of sapphire was conducted and effect of KOH etching time on the device performance of the fabricated Schottky diodes was also investigated. Vertical-structured GaN SBDs with die size of $400\times 400$ μm2 and Schottky contact area of 200 μm in diameter have been successfully fabricated. The extracted values of Schottky barrier height ($\Phi_{\text{B}}$), series resistance ($R_{\text{s}}$), and ideality factor ($\eta$) of the 60-s-KOH etched SBDs were 0.78 eV, 1.9 m$\Omega$, and 1.06, respectively.
2006-06-25