多孔硅的孔隙对硫化锌／多孔硅光电性质的影响

Influence of porous silicon porosity on optoelectronic property of ZnS/porous silicon

为了研究衬底多孔硅(PS)的孔隙对硫化锌/多孔硅(ZnS/PS)复合体系的光学性能和电学性质的影响,采用脉冲激光沉积方法在不同孔隙度的PS衬底上沉积了硫化锌薄膜。利用X射线衍射仪、扫描电子显微镜、荧光分光光度计和Ⅰ-Ⅴ特性曲线分别研究了PS衬底上ZnS薄膜的晶体结构、表面形貌和ZnS/PS复合体系的光学和电学性质。结果表明,沉积的ZnS薄膜呈立方相晶体结构,沿β-ZnS(111)晶向择优取向生长。随着衬底PS孔隙的增多,ZnS薄膜衍射峰的强度减小,且薄膜表面出现一些空洞和裂缝;在ZnS/PS复合体系的光致发光谱中,PS的发光相对于未沉积ZnS薄膜的PS有所蓝移,随着PS孔隙的增多,该蓝移量增大,而且在光谱中间550nm左右出现了一个新的绿光发射,归因于ZnS的缺陷中心发光。ZnS的蓝、绿光与PS的红光相叠加,整个ZnS/PS复合体系呈现出较强的白光发射。ZnS/PS异质结的Ⅰ-Ⅴ特性曲线呈现出与普通二极管相似的整流特性,在正向偏置下,电流密度较大,电压降较低;在反向偏置下,电流密度接近于0。随着衬底PS孔隙的增多,正向电流增大。该项研究结果为固态白光发射器件的实现奠定了基础。

In order to study effect of porous silicon （PS） porosity on the optical and electrical properties of ZnS/PS composites, ZnS film was deposited on PS substrates with different porosities by means of pulsed laser deposition. The crystalline structure, surface morphology of ZnS film on PS substrates and optical, electrical properties of ZnS/PS composites were studied by means of X-ray diffraction, scanning electron microscope, photolumineseence （PL） spectra and 1-V characteristics respectively. The resuhs show that ZnS film deposited on PS substrates have a crystalline structure of cubic phase growing in preferred orientation along 13-ZnS（ 111 ）direction. With the increase of PS substrate porosity, the intensity of diffraction peak of ZnS film decreases and some voids and cracks appears in ZnS film. In the PL spectra of ZnS/PS composites, the PL peak of PS has a blue shift compared with original PS. The larger the porosity of PS substrate, the greater the blue shift. With the increase of PS substrate porosity, a new green light emission at about 550nm appears which is attributed to defect-center luminescence of ZnS. The blue, green emission of ZnS combined with the red emission of PS, ZnS/PS composites exhibit intense white light emission. Based on the 1-V characteristics, ZnS/PS heterojunctions exhibit the similar rectifying properties to the common diode. Under forward bias conditions, the current density is large and the voltage drop is small, on the contrary, under reverse bias conditions, the current density is nearly zero. With the increase of PS substrate porosity, the forward current increases. The research results lay a foundation for the realization of solid state white light emission devices.