氮化铝薄膜的光学性能

分别使用X衍射仪和紫外（190 nm～800 nm）分光光度仪,测量了用分子束外延法生长在SiC（001）基底面上的AIN薄膜的X衍射、透射谱和不同温度下的吸收谱.X衍射表明:实验所用的AIN薄膜在c-轴存在应变和应力，该应变和应力主要是由于AIN的晶格常量与基底SiC的晶格常量不匹配所致.透射谱表明:AIN薄膜的禁带宽度大约为6.2eV；而其对应的吸收谱在6.2eV处存在一个明显的台阶,此台阶被认为是AIN薄膜中的带边自由激子吸收所产生,忽略激子的结合能(与禁带宽度相比),则该值就对应为AIN的禁带宽度.而其对应的不同温度下（10 k～293 k）的吸收谱的谱线的形状和位置无明显的变化表明:温度对AIN薄膜的禁带宽度亦无明显的影响，这主要是由于在AIN薄膜中存在着应力所致.

The Optical Properties of AIN Film

An X-diffraction,a transmittance spectrum and absorption spectrums at different temperatures of an AIN film deposited on a(001) SiC substrate by MBE were measured on a X-diffractometer and an UV spectrophotometer(190nm～800nm) respectively. The X-diffraction spectrum shows that: there are strains in the c-axial orientation of the AIN,these sstrains are caused by the dismatching of crystal lattice constant of the AIN and the SiC substrate,and these stains will cause the stresses in the AIN film;the transmitrtance spectrum of the AIN shows that: the direct-band-gap of the AIN is about 6.2 eV;and obvious“knees”or a“shoulders”structure around 6.2 eV existing in the absorption spectrums are considered to the caused by the free excitonic absorptions in the AIN film,if not considered the formation energy of the free exciton,6.2 e is the value of the direct-band-gap of the AIN film;the“kness”or the“ shoulder”structure and position don't change with the temperature in the absorption spectrums of the AIN shows that: the temperature doesn't influence the value of the direct-band-gap of the AIN obviously,this is probable,which is caused by the stresses existing in the AIN film.