摘要
以去离子水(H2O)和二乙基锌(DEZn)为源材料,生长温度是680℃时,利用常压MOCVD在GaN/A l2O3模板上成功生长了ZnO单晶薄膜,用原子力显微镜(AFM)、X射线双晶衍射(DCXRD)、光致发光谱(PL)对ZnO薄膜的表面形貌、结晶学性质、光学性质作了综合研究。双晶衍射表明,ZnO非对称(101-2)面ω扫描的半峰全宽(FWHM)仅为420 arcsec,估算所生长ZnO膜的位错密度大约为108/cm2量级,这与具有器件质量的GaN材料的位错密度相当。在ZnO薄膜的低温15 K光荧光谱中,观察到很强的自由激子和束缚激子发射以及自由激子与束缚激子的多级声子伴线。
ZnO, a wide direct-gap semiconductor, attracts as much attention as GaN in optoelectronics research field. Recently, there has been a great progress in the growth of ZnO thin films. But applicable ZnO optoelectronic devices have not been fabricated yet, mainly due to that sufficiently effective p-type ZnO thin films have not been obtained up to now. To solve the p-type doping problems, it is necessary to grow higher quality ZnO thin films. One of the key issues to grow high quality ZnO thin films is to find a lattice matched substrate. GaN and ZnO have close lattice constant and the mismatch of them is less than 2%, so GaN is the suitable substrate for the growth of ZnO epitaxial layers. At present, the technique of growing high quality GaN films on Al2O3substrate has developed mature through the research of more than ten years, it is a feasible method to use the GaN epilayer as the buffer layers on other substrates for the growth of ZnO epitaxial layers. ZnO films used in this study were grown by a home-built vertical atmospheric pressure MOCVD system. The GaN/Al2O3 templates were fabricated by a low-pressure MOCVD system （Thomas Swan, CCS）. The thickness of the GaN layer was abont 3 mm. We used deionizcd water and Zn（ C2H5 ）2 as the O and Zn sources, respectively, and nitrogen as the carrier gas. The thickness of the ZnO layer is 2 μm. ZnO epilayer characteristics were investigated by AFM, DCXRD and PL. XRD spectra showed that the threading dislocation density of the ZnO films is in the order of 10s cm^-2, which is comparable to device-level GaN films. The ZnO films showed very bright near band-edge luminescence is at 3. 263 eV at room temperature and the deep-level emission is quite weak in the whole spectrum. The absence of the deep-level emission peak indicates that the ZnO films are of excellent optical quality and have few interior defects. From the low temperature PL spectrum, the domination of free exciton and the appearance of its two replicas strongly further prove the high quality of the ZnO films. This superior optical feature is an indication of the potential of atmospheric pressure MOCVD for ZnO growth on epi-GaN/Al2O3 templates.
出处
《发光学报》
EI
CAS
CSCD
北大核心
2005年第6期772-776,共5页
Chinese Journal of Luminescence
基金
国家"863"计划纳米专项(2003AA302160)
电子发展基金(2004125)资助项目
