退火对6H-SiC晶体的光学性质及光致发光的影响

Influence of annealing on optical properties and photoluminescence of 6H-SiC crystal

利用双光束分光光度计对高温退火前后的掺氮和未掺杂6H-SiC晶体的透射及反射谱进行了分析,发现无论退火前后,两种SiC晶体在紫外区均存在强烈的吸收。在可见和近红外区,尤其是未掺杂SiC样品具有很高的透射率,退火后,两种样品的透射率均明显提高。利用荧光分光光度计研究了退火前后样品的光致发光特性,结果表明:在390 nm Xe灯激发下,两种样品在417 nm和436 nm处均可观察到蓝光发射,417 nm处的发光归结于C簇的发光,436 nm处的发光机理为从晶粒的核心激发载流子转移到晶粒表面,并与其上的发光中心辐射复合;同时,掺氮SiC在575 nm处还存在发光峰,为氮掺入后引起的非晶SiC的发光,在325 nm Xe灯激发下,525 nm处存在发光峰,其详细发光机制有待进一步研究。

Using the double beam spectrophotometer,transmission and reflection spectra of 6H-SiC crystal were analyzed before and after high temperature annealing.It is found that both kinds of the SiC crystals in the ultraviolet region existed a strong absorption,whereas in the visible and near infrared region,the non-doped SiC sample had a high transmittance.After annealing,the transmittance of two samples improved significantly.Fluorescence spectrophotometer analysis,excited at the 390 nm line of a Xe lamp,showed that a blue double-peak（417 and 436 nm） photoluminescence was presented in both samples.The 417 nm emission was due to C cluster and the 436 nm emission was attributed to the radiation of carrier recombination.These carriers were excited from the core of the SiC crystal particles tothe photoluminescent centers of the surface of the SiC crystal particles.Furthermore,nitrogen-doped SiC showed a peak at 575 nm,which was the light-emitting of amorphous SiC caused by nitrogen doping.Another PL peak at 525 nm may occur under the 325 nm line excitation of the Xe lamp,whose light-emitting mechanism remains to be further studied.