||Jong Hoon Lee, Hong Seung Kim, Bo Ra Jang, Ju Young Lee, Nak Won Jang, Bo Hyun Kong, Hyung Koun Cho, Won Jae Lee
ZnO material is attractive for using optical devices, solar cells, transparent conducting oxide electrodes, and transparent thin film transistors because of its wide band gap (3.37 eV) energy and large exciton binding energy (60 meV). Recently, although the results of p-type ZnO film have been reported, it is still difficulty to growth of reliable p-type ZnO material due to the low solubility of the dopant and the highly self-compensating process upon doing. For these reasons, the p-n junction structure have attempted with other p-type materials such as p-GaN, p-SiC and p-Si. Especially, the p-type silicon substrate has various advantages such as large area substrate, low cost and excellent Si-based technology. An un-doped ZnO material has dominant n-type conductivity at room temperature due to the native defects such as zinc interstitials (Zn<sub>i</sub>) and oxygen vacancies (V<sub>o</sub>), or present of hydrogen. A study of the ZnO about the carrier concentration is to obtain high carrier concentration (over 10<sup>20</sup> /cm<sup>3</sup>) for substitution of indium tin oxide. The high carrier concentration of n-type ZnO can be obtained as high doping (over 1 at. %) in the ZnO with group Ш donor impurities such as Ga, Al and In. As the p-n junction diode need to the properties of semi-conductor, we attempted low doping in the ZnO films with indium (0.6, 1, 5, and 10 at. %) for a stable n-type properties on diode characteristics. In this work, our aim is to investigate relationship between changed dido characteristics and effect of In-doping in the ZnO. The In-doped ZnO was deposited by using a pulsed laser deposition system with In-doped ZnO target. The structural characteristics of In-doped ZnO films were investigated by XRD and TEM. The electrical properties of In-doped ZnO films were measured by Hall measurement and the diode characteristics were investigated by current-voltage measurement. The electrical properties of In-doped ZnO films were changed to increase the carrier concentration up to 3.0 × 10<sup>19</sup> and to decrease resistivity up to the 1.5 × 10<sup>-2</sup> Ω-cm. Also, the diode characteristics were considerably change by the effect of In-doping. Especially, In-doped ZnO/p-Si diodes show very low reverse current density about 2.8 × 10<sup>-6</sup> A/cm<sup>2</sup> (In 10 at. %) at -5 V and high on-off ratio (In 10 at. %) about 2.5 × 10<sup>-6</sup> at ±5 V. The hetero structure diode exhibited typical current-voltage behaviors with turn-on voltages of 1.8 ~ 4.6 V and with series resistance of 37 ~ 99 Ω. The different diode characteristics may be related on the changed structures of ZnO films by indium doping and we discuss about the relationship between the diode characteristics and the effect of In-doping in the ZnO films. (NIPA-2009-C1090-0903-007 & Human Resource Training Project for Strategic Technology).