利用分子束磊晶成長硒化鋅於矽奈米溝槽及硒化鋅所受應變分佈研究

Abstract

以分子束磊晶成長硒化鋅於矽基板上的不同寬度之奈米溝槽中，磊晶開始以鋅流量遠大於硒流量之方式成長以避免硒化矽形成，並且分別成長4、8與12小時以獲得相對為120、243與386奈米厚的硒化鋅。藉由量測拉曼光譜縱向光學聲子半高全寬驗證溝槽內之硒化鋅的磊晶品質優於外圍的硒化鋅薄膜。並且分析硒化鋅橫向光學聲子之拉曼位移，得知隨著厚度增加樣品的伸張應變越小。而比較不同寬度的樣品時(1500奈米及1000奈米)，寬度較窄的溝槽中其硒化鋅所受伸張應變也較小。 最終，以變溫光激螢光光譜推測在成長溫度573 K的情況下，硒化鋅所受到的應變會變為壓縮應變，寬度較窄的溝槽中其硒化鋅壓縮應變會大於溝槽寬度較寬者，此乃由於在較窄的溝槽中缺陷較少使得應力釋放不完全所致。

ZnSe nano-structures were grown in Si nano-trenches of various widths by molecular beam epitaxy. At the initial growth stage, high Zn/Se flux ratio was used for preventing the formation of SiSex compounds. The growth time for ZnSe was controlled to be 4hr, 8hr and 12hr for the respective thicknesses of 120, 243, and 386 nm. In the Raman scattering spectra, the full width at half maximum (FWHM) of the longitudinal optical (LO) phonon of ZnSe in the trench is smaller than that of ZnSe on SiO2. It implies ZnSe grown in the Si nano-trench has better crystal quality. The strain distribution was analyzed by calculating the Raman shift of the transverse optical (TO) phonon. The tensile strain decreases with the increasing thickness of ZnSe. As the width of trench decreases from 1500nm to 1000nm, the tensile strain decreases from 0.37% to 0.26%, respectively. The temperature dependent photoluminescence measurement reveals that the tensile strain becomes compressive strain as the temperature increases from low temperature to the growth temperature (573 K). The compressive strain for ZnSe at 573 K is larger in the narrower trench due to the smaller amount of defects in narrower trench (1000nm).