在矽基板上成長矽鍺、砷化鎵及硒化鋅異質結構之研究

Abstract

磊晶成長異質結構於矽基板上是非常熱門且有價值的研究，但由於矽的晶格常數與鍺、砷化鎵及硒化鋅約有4.2% 以上的晶格不匹配，因此無法直接在矽基板上磊晶成長出高品質的鍺、砷化鎵及硒化鋅等異質結構。在此研究中，我們利用矽鍺半導體材料當作成長鍺磊晶層的成長緩衝層，藉由改變在矽鍺磊晶層中的鍺含量使其最終達到純鍺磊層。為了有效降低鍺磊晶層中的缺陷密度，我們提出了應變能界面侷部控制與阻擋技術，其中應變能界面是由兩層適當鍺含量磊晶層之界面應力場產生（兩層鍺含量差約5%），此應力場可以彎曲並阻擋線缺陷的傳遞。利用此技術我們成功的在矽基板上成長了高品質的鍺磊晶層。鍺磊晶層的缺陷密度約3×106 cm-2，總磊晶厚度小於2.6μm，表面粗糙度約3.2Å。此外，我們也利用MOCVD及MBE成長技術結合鍺/矽鍺緩衝層，成功的將具有優良光或電特性的砷化鎵及硒化鋅異質材料磊晶成長於矽基板上。實驗結果顯示，砷化鎵磊晶層的缺陷密度接近3×106 cm-2，總磊晶厚度小於5μm。硒化鋅磊晶層的缺陷密度接近3×106 cm-2，總磊晶厚度小於5μm，光學特性接近塊材的硒化鋅材料。此方法的好處為可以改善在矽基板上製作異質結構元件的導熱性、提高製造率、降低製造成本又可與成熟之矽製程技術相容。基於這些特性，此研究結果對未來將光及電元件整合於同一矽晶片上提供一個新的思考方向。

An interface-blocking mechanism was proposed to reduce the threading dislocations in the SiGe and Ge layers grown on the Si (100) substrates. In this study, epitaxial Si1-xGex/ Si1-(x-y)Gex-y and Ge/ SiyGe1-y layers were grown by UHV/CVD. It was found surprisingly that if the Ge composition, y, was varied across the interface of Si1-xGex/ Si1-(x-y)Gex-y or Ge/ SiyGe1-y above a certain value, most of the threading dislocations appear to be blocked and confined in the underlying Si1-(x-y)Gex-y or SiyGe1-y layer by the interface. This finding provides a simple way to grow high-quality relaxed SiGe and Ge layers on the Si substrates. The growth of high-quality epitaxial Ge layers on a Si (100) substrate was demonstrated by using this method. Experimental results showed that the dislocation density in the top Ge layer was greatly reduced, and the surface was very smooth, while the total thickness of the structure was only 2.6μm. It implies that this finding can provide a virtual substrate for growing GaAs and ZnSe on Si. The growth of the high-quality GaAs and ZnSe layers on the Ge/GexSi1-x/Si virtual substrates is demonstrated in this work with the dislocation density of GaAs and ZnSe about 3×10-6 cm-2 and the epitaxial layers also show a excellent optical characteristics. The total thickness of the GaAs/Si and ZnSe/Si was only 5.1□m.