脉冲激光沉积(PLD)法生长高质量ZnO薄膜及其发光性能

采用脉冲激光沉积(PLD)法在单晶Si(100)衬底上生长ZnO薄膜,以X射线衍射(XRD)、原子力显微镜(AFM)和透射电镜(TEM)等手段分析了所得ZnO薄膜的晶体结构和微观形貌。优化工艺(700℃,20Pa)下生长的ZnO薄膜呈c轴高度择优取向,柱状晶垂直衬底表面生长,结构致密均匀。室温光致发光(PL)谱分析结果表明,随着薄膜生长时O₂分压的增大,近带边紫外发光峰与深能级发光峰之比显著增强,表明薄膜的结晶性能和化学计量比都有了很大的改善。O₂分压为20Pa时所生长的ZnO薄膜具有较理想的化学计量比和较高的光学质量。

Growth and Photoluminescence Characteristics of High Quality ZnO Films by Pulsed Laser Deposition (PLD) Method

ZnO has recently become a very popular material due to its great potential for optoelectronics applications. The large direct band gap of 3.3 eV, along with the large exciton binding energy (60 meV) and many other advantages, make ZnO a strong candidate for the next generation of ultraviolet light emitting and lasing devices operating at high temperatures and in harsh environments. The ZnO based light emitting diode (LEDs) will be brighter than the current state-of-art nitride light emitters, and at the same time, the production cost will be reduced significantly compared with current technology. The pulsed laser deposition (PLD) technique has been proved to be a very effective method to deposit high-quality films with complex composition. This technique has some other advantages such as deposition in controllable oxygen partial pressure, high controllability of film composition and growth process, and relatively high deposition rates. In this paper, the ZnO films were deposited on single-crystalline Si(100) substrates by pulsed laser deposition (PLD) method. X-ray diffraction (XRD),atom force microscope (AFM),transmission electron microscope (TEM)and photoluminescence (PL) spectrum measurements were employed for the investigation of crystal quality and light emitting performance. The dependence of crystal quality and photoluminescence performance on the growth temperature and oxygen partial pressure was investigated. The results indicate that high-quality ZnOthin films with perfect c-axis preferred orientation and smooth and dense microstructure have been successfully grown under optimized conditions (700℃, 20 Pa). The near-band-edge emissions in PL spectra are greatly enhanced and the deep level emissions are weakened with the increase of oxygen pressure due to the improvement of stoichiometry, the ZnO films grown under high O₂ pressure (20 Pa) are well close to stoichiometry and of optically high quality. Therefore, it can be concluded that the PL spectra depend on the stoichiometry and the microstructure of the film. The achievement reported here will be used to control the optical properties of ZnOthin films for optical device applications.