超高真空熱蒸鍍系統架設以及以超高真空熱蒸鍍技術成長硒化鋅薄膜之特性研究

Abstract

利用超高真空熱蒸鍍技術，分別於玻璃以及(100)砷化鎵基板上成長硒化鋅薄膜。藉由X-ray繞射以及光激螢光光譜量測來分析薄膜的品質。於ZnSe/Glass上，XRD證實薄膜為高度傾向[111]方向排列的多晶zinc-blend結構；並且估算出薄膜的晶格常數以及晶粒大小分別為 與 。於ZnSe/GaAs上，我們將不同熱處理溫度(505℃隹℃)下所成長的ZnSe/GaAs薄膜，以PL量測分析。發現505℃下成長的薄膜(sample 0719)，有相當明顯的激子結構(I1、I2、FX)，並有因雜質所造成的譜線( )與深層放射光譜分佈(SA band) ；而在585℃下成長的薄膜(sample 0524)，則有因Ga施子與Li或Na等受子復合所造成的DAP放射。此外，藉由XRD光譜，分析不同成長溫度(310℃闎℃)下所成長的ZnSe/GaAs，發現350℃下的薄膜顯然具有較強且半高寬較為狹窄的ZnSe繞射光譜。

ZnSe thin films were grown on glass and (100) GaAs substrates by thermal evaporation in UHV situation. X-ray diffraction and photoluminescence measurements are employed to analyze the quality of the grown films. XRD confirmed that the film grown on the glass substrate is in zinc-blende polycrystalline structure with high orientation in [111] direction； the lattice constant and the grain size were estimated to be and , respectively. Photoluminescence(PL) measurements were used to study the property of these films, such as chemical impurities and native defects in the ZnSe /GaAs films with which GaAs substrates were outgassed at 505℃(sample 0719) and 585℃(sample 0524), respectively before ZnSe films were grown on these substrates. The spectrum of sample 0719 shows a rich excitonic structure associated with neutral donor-bound excitons I2, neutral acceptor-bound excitons I2 and free excitons FX, and the peaks related to impurities involving the line and the deep level emission SA. The peak in PL spectra at ~2.7eV was observed only for the sample 0524, it is believed that this peak is associated with donor-acceptor transitions which originated from the radiative recombination between a Ga donor and a contaminated Li and Na acceptor. ZnSe/GaAs films with different grown temperatures (310℃闎℃) were characterized by DCXRD. We discovered that the films grown at 350℃ showed the stronger ZnSe peak with a smaller FWHM value than that grown at 310℃.