Effect of Indium Mole Fraction on the Diode Characteristics of ZnO:In/p-Si(111) Heterojunctions

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We investigated the effect of indium (In) doping (0.6, 1, 5, and 10 at. %) on the diode characteristics of heterostructures consisting of In-doped ZnO films on p-Si(111) substrates. In-doped ZnO films were deposited by pulsed laser deposition with an In-doped ZnO target, and heterojunction diodes were fabricated by photolithography and a lift-off method. The electrical properties of ZnO films were altered by In doping, with the In (10 at. %)-doped ZnO film having the highest electron concentration ($3.0\times 10^{19}$ cm-3) and lowest resistivity ($1.5\times 10^{-2}$ $\Omega$$\cdot$cm) of the analyzed ZnO films. In doping also had a strong effect on diode characteristics. In particular, In-doped ZnO/p-Si diodes show a very low reverse current density of approximately $2.8\times 10^{-6}$ A/cm2 (In 10 at. %) at $-5$ V and a high on--off ratio (In 10 at. %) of about $2.5\times 10^{-6}$ at $\pm 5$ V. The heterostructure diodes exhibited typical current--voltage characteristics with turn-on voltages in the range 1.2--2.4 V and series resistances in the range 37--99 $\Omega$. The modified diode characteristics may be related to changes in the ZnO film structure induced by In doping. We also discuss the effect on diode characteristics of In doping of ZnO films.
2011-03-25