SiH_2Cl_2-NH_3配比对a-SiN_x∶H薄膜PL峰的影响

Photoluminescence Properties of Silicon-rich SiN_x Films Deposited from the SiH_2Cl_2-NH_3 Reactant Mixture in LPCVD

低压化学气相沉积制备的纳米硅镶嵌结构的a-SiNx:H薄膜,在3.75 eV的激光激发下,室温下发射1～3个高强度的可见荧光.在相同的沉积温度下(900℃),选择不同的SiH2Cl2和NH3气体配比时,所得薄膜表现出不同的荧光属性,荧光峰的峰位和数目有着显著的变化.通过TEM、IR、XPX等分析手段对其原因进行了研究分析,认为不同配比下,生成的薄膜中缺陷态的种类和密度有所不同,这影响了其PL峰个数及其各峰的相对强弱.

Many experiments have reported that the silicon-rich silicon nitride thin films can emit strong visible light at room temperature, at light excitation, and the silicon-rich silicon nitride thin films were usually prepared through plasma enhanced chemical vapor deposition （PECVD） technology or low pressure chemical vapor deposition （LPCVD） technology, among which the thin films made by PECVD technology was used and researched more often, for the lower temperature. Yet the silicon nitride thin films obtained by LPCVD have many advantages than the silicon nitride thin films by PECVD, including higher refractive index, higher density, higher resistivity, higher breakdown field, higher band gap and so on. Moreover, although experiments concluded all the silicon nitride thin films showing photoluminescence have mosaic structure of silicon nanodots embedded in amorphous silicon nitride films, the size and the number of silicon nano-dots is quite different in the films made by LPCVD and PECVD, which means they may have different luminescence mechanics. So our team has researched the photoluminescence mechanics of silicon nitride films prepared by LPCVD in the last year. By choosing different deposition condition during the samples preparing, the microstructure and the defects of the thin films can be changed, as a result, the PL spectrum will change consequentially. Using TEM, IR and XPS, the luminescence mechanics of the silicon nitride thin films were investigated. We changed the ratio of dichlorosilane to ammonia, keeping the deposition temperature at 900 ℃. The result shows quite different PL spectra, and we has explained the results using our gap states model.