退火对ZnO薄膜晶体结构和ZnO/p-Si异质结光电性质的影响

Influence of Annealing on ZnO Films and ZnO/p-Si Heterojunctions

采用脉冲激光沉积方法在p-Si(100)衬底上生长ZnO薄膜,分别在500℃、600℃和700℃下真空退火,采用X射线衍射仪研究了退火对ZnO薄膜晶体结构的影响,并测量了ZnO的面电阻和ZnO/p-Si异质结的I-V特性曲线。研究表明,随着退火温度的升高,ZnO的(002)衍射峰强度逐渐增大,半峰全宽不断减小,同时薄膜内应力减小,ZnO晶粒尺寸变大。表明高温退火有助于ZnO薄膜结晶质量的提高。在没有光照的条件下,异质结的漏电流随退火温度的增加而增大;用650 nm光照射样品时,600℃退火的样品表现出最明显的光电效应,而过高的退火温度会破坏ZnO/p-Si异质结的界面结构,使其光电流变小。所以,要得到性能良好的光电器件,应选取适当的退火温度。

ZnO films were deposited on p-Si （100） substrate by pulsed laser deposition （PLD）. Then the samples were annealed at 500℃, 600℃ and 700 ℃ respectively. X-ray diffraction （XRD） was employed to analyze the effects of annealing on the crystalline structure of the ZnO films. The sheet resistance of the ZnO films and the I-V characteristics of the heterojunctions were also studied. The results show that higher annealing temperature enhances the films＇ crystal quality. The intensity of the （002） diffraction peak increases and the full width at half maximum （FWHM） decreases with the rise of annealing temperature, mean while, the internal stress in film decreases and the ZnO crystal grain size increases. Without light illumination, the dark leakage current of the heterojunctions increases with the rise of annealing temperature. With illumination of 650 nm light, the best photoelectric effect is obtained from the sample annealed at 600 ℃ . It is revealed that the interface of the heterojunctions might be degraded at higher annealing temperature. Therefore, proper annealing temperature is necessary for high quality photoelectric devices.