以原子層磊晶技術在有機金屬氣相化學沉積機台成長砷化鎵於鍺基板上之研究

Abstract

本論文研究乃在鍺基板上用原子層磊晶技術(Atomic Layer Epitaxy, ALE)法成長砷化鎵層為成核層(Nucleation layer)。實驗結果顯示當成長溫度過低時(415℃)，因TMGa裂解率偏低，導致表面會呈現三角形的缺陷；當磊晶溫度在420℃下成長10對鎵/砷磊晶層將使表面粗糙度降至1.22nm，也能改善磊晶品質(15arcsec)。根據AES分析結果可知當成長溫度為420℃時所成長砷化鎵/鍺異質結構不會產生內部擴散的問題。於鎵與砷層間增加適當吹氣時間(20秒)也可增加砷化鎵/鍺異質結構磊晶品質，吹氣時間太長會導致已經成長上去砷原子自表面脫附，進而使砷化銦鎵/鍺磊晶品質變差。此研究成果證實在低溫成長條件下使用原子磊晶技術法成長砷化鎵磊晶層於Ge基板上，可降低砷、鎵、鍺原子擴散及平坦表面，將有助於取代傳統磷化銦鎵的使用。

GaAs epitaxy, as nucleation layer, is grown on Ge substrate using ALE technique (Atomic Layer Epitaxy). According our study, triangle defects are formed on the surface of (In)GaAs/Ge due to lower decomposition rate of TMGa at low growth temperature (415°C). For ALE technique, the multilayer consisted of 10 pairs of Ga and As layers can improve epitaxial quality (15 arcsec) and surface morphology (1.22nm) of (In)GaAs/Ge heterostructure at 420°C. The growth temperature of 420°C is also adopted to suppress unwanted interdiffusion during (In)GaAs/Ge heterostructure growth. Moreover, long purge time (＞20sec) results arsenic desorption from the surface of ALE-GaAs epitaxy and affects epitaxial quality during InGaAs/GaAs/Ge heterostructure growth. It is demonstrated that GaAs nucleation layer grown on Ge substrate using ALE technique has great potential to replace InGaP layer of traditional III-V solar cell for suppressing unwanted interdiffusion and producing smooth surface morphology.