利用分子束磊晶法在氮極性面與鎵極性面之氮化鎵上成長異質結構CuInSe2之特性研究

Abstract

我們嘗試在氮化鎵上成長銅銦硒CuInSe2 (CIS)薄膜，分析富銅(Cu-rich)和富銦(In-rich) 的CIS成長於鎵極性面與氮極性面的薄膜品質與成長特性，我們利用原子力顯微鏡(AFM)觀察表面形貌，Cu-rich CIS表面較粗糙且粒徑較大。透過穿透光譜分析可以估算富銅與富銦的CIS能隙分別為1.045 eV與1.063 eV。XRD 的搖擺曲線分析Cu-rich CIS薄膜半高寬為897.8 arcsec，且透過Phi scan印證我們成長於氮化鎵的CIS結構為黃銅礦結構，其方向為(112)。利用穿透電子顯微鏡(TEM)分析CIS與氮化鎵的微結構，可以觀察到CIS會產生Rotation twin缺陷來釋放成長時所受的壓應力，並且觀察到富銦的情況下會產生多晶結構與傾斜晶等結構，使富銦的CIS品質不佳。我們利用區域磊晶理論(Domain Epitaxy)解釋在晶格不批配高達28.5%卻可以成長高品質的CIS薄膜於氮化鎵上，其區域不批配度約為2.8%。由能量散佈光譜(EDS)分析可以證明CIS與GaN界面沒有擴散現象與交互作用。由拉曼光譜分析可以再次驗證我們成長的CIS薄膜為黃銅礦結構。我們成功的將CIS(112)黃銅礦結構成長於氮化鎵(000±1)上，相信在未來可以應用於更多的光電元件。

We have studied that chalcopyrite CuInSe2 thin films were grown on GaN (000±1) by molecular beam epitaxy (MBE). Atomic Force Microscopy (AFM) was used for characterizing the surface morphology and surface roughenss. Cu-rich CIS has a bigger grain size and surface roughenss. The band gap of Cu-rich CIS and In-rich CIS were evaluated by spectrophotometer. The absorption edge of Cu-rich CIS is at 1187 nm, which equals to the band gap of 1.045eV. The absorption edge of In-rich CIS is at 1166 nm, which equals to the band gap of 1.063eV. X-ray diffraction showed that the CuInSe2 thin film was grown in (112) orientation. The Cu-rich CuInSe2’s peak of rocking curve with full width at half maximum of about 897.8 arcsec indicated the epitaxial growth of Cu-rich CuInSe2(112) film on N-face GaN substrate. Microstructure analysis of the CuInSe2 showed that the large lattice mismatch (28.5%) between CuInSe2 and GaN is accommodated by domain epitaxy, and domain mismatch is about 2.8%. We found that there has no interface reaction or diffusion occurs between CuInSe2 and GaN by Energy-Dispersive Spectroscope(EDS). Our experimental results show that the heteroepitaxially grown CuInSe2 on GaN is stable, which exhibits a great potential for optoelectronic applications.