| 초록 |
ZnO epilayer was synthesized by the pulsed laser deposition(PLD) process on Al2O3 substrate after irradiating the surface of ZnO sintered pellet by ArF(193 nm) excimer laser. The epilayers of ZnO were achieved on sapphire(Al2O3) substrate at the temperature of 400 oC. The crystalline structure of epilayer was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of ZnO epilayer measured with Hall effect by van der Pauw method are 8.27×1016 cm-3 and 299 cm2/V-s at 293K, respectively. The temperature dependence of the energy band gap of the ZnO obtained from the absorption spectra was well described by the Varshni's relation, Eg(T) = 3.3973 eV - (2.69 × 10-4 eV/K)T2/(T + 463K). After the as-grown ZnO epilayer was annealed in Zn atmospheres, oxygen and vaccum the origin of point defects of ZnO atmospheres has been investigated by the photoluminescence(PL) at 10 K. The native defects of VZn, VO, Znint, and Oint obtained by PL measurements were classified as a donor or acceptor type. In addition, we concluded that the heat-treatment in the oxygen atmosphere converted ZnO thin films to an optical p-type. Also, we confirmed that vacuum in ZnO/Al2O3 did not form the native defects because vacuum in ZnO thin films existed in the form of stable bonds. |
