籽晶层对喷雾热分解法生长ZnO薄膜结晶质量和光电性能的影响

Effect of Seeding Layer on the Crystal Quality and Photoelectric Property of ZnO Films Grown by Spray Pyrolysis

通过脉冲激光沉积(PLD)方法在Si(100)衬底上沉积一层高质量的ZnO籽晶层,在籽晶层上进一步采用超声喷雾热分解(USP)法生长ZnO薄膜,研究了籽晶层对ZnO薄膜结晶质量和ZnO/Si异质结光电特性的影响。研究结果表明,在籽晶层的诱导作用下,USP法生长ZnO薄膜由多取向结构变为(002)单一取向,结晶性能得到了显著改善;籽晶层上生长的薄膜呈现出垂直于衬底生长的柱状晶结构,微观结构更加致密。通过研究紫外光照前后ZnO/Si异质结的整流特性,发现引入籽晶层后,反向偏压下异质结的光电响应显著增加,并且在开路状态下出现明显的光伏效应。

ZnO is a novel wide band gap semiconductor material for optoelectronic applications and has received extensively attention in recent years. The growth of high quality ZnO materials and p-type doping for ZnO films are key techniques for the development of ZnO based optoelectronic devices. Our previous study shows that ZnO films grown by ultrasonic spray pyrolysis （USP） can easily be doped to p-type, and the resulting p-type film exhibits low resistivity and high hole concentration. However, USP method is difficult to grow ZnO films with high quality crystal structure, which limits the application of ZnO films by USP. In this paper, we aim to improve the crystallinity of the USP-grown ZnO films by introducing a high quality ZnO seeding layer. We firstly deposited a ZnO seeding layer On Si（100） by pulsed laser deposition （ PLD）, and then grew ZnO film on the seeding layer by USP method. The ZnO seeding layer by PLD shows high quality crystal structure with highly （002） orientation and atomic scale smooth surface. The effect of ZnO seeding layer on the crystal quality and photoelectrical properties has been studied. Results indicate that by the induction of the seeding layer, ZnO film changes from multi-oriented polycrystalline structure to highly （002） oriented structure with significantly enhanced crystallinity. The resultant film possesses columnar microstructure perpendicular to the substrate and exhibits smooth, dense and uniform morphology. In order to characterize the photoelectric properties of ZnO films, we measured the photoelectric response of ZnO/Si heterojunction. It is concluded that ZnO/Si heterojunction formed by ZnO film with seeding layer exhibits markedly higher photocurrent at reverse bias and significant pen-circuit photovoltage at UV illumination, compared with the heterojunction by ZnO film without seeding layer. The present study provides a good starting point for preparation of p-type ZnO films with both excellent electrical properties and high quality crystal structure.