以電漿輔助式分子束磊晶法成長氧化鎂鋅磊晶薄膜與特性研究

Abstract

以氧化鎂及低溫氧化鋅做為緩衝層，利用電漿輔助式分子束磊晶系統在 藍寶石(0001)基板上成長氧化鋅與氧化鎂鋅磊晶薄膜。針對氧化鋅薄膜成長 調變鋅原子/氧離子流量比，研究氧化鋅薄膜的表面型態和光學特性。當鋅 流量為1.5×10-7 Torr 時，表面粗糙度約為0.5 nm，光激螢光訊號半高寬為 4.7 meV。而對於氧化鎂鋅薄膜成長，藉由調變鎂/鋅比例，研究表面粗糙度 及光學特性。當鎂含量增加時，表面粗糙度會呈現近線性增加，光激螢光 訊號會藍移到高能量。在鎂莫耳濃度為0.132 時，表面粗糙度為2.3 nm，發 光能量在3.603 eV，半高寬為41.4 meV。綜合氧化鋅和氧化鎂鋅磊晶薄膜 的結果，證明適當的II 族元素對VI 族元素流量比、加上低溫緩衝層及熱退 火可以改善薄膜平整度及光性。此研究可應用於製作高品質氧化鋅/氧化鎂 鋅多重量子井結構。

ZnO and ZnMgO epitaxial films were grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy using MgO and low temperature-ZnO buffer layers. The dependence of surface morphology and emission properties of ZnO epilayers on Zn/O flux ratios was investigated. The root mean square (RMS) roughness of high quality ZnO epitaxial film is only 0.5 nm and the full width at half maximum (FWHM) of PL emission peak is 4.7 meV for Zn flux of 1.5×10-7 Torr. For the Zn1-xMgxO epilayers grown at various Mg/Zn ratios, the roughness increases nearly linearly and the emission energy exhibits blue-shift when Mg concentration increases. At x=13.2%, the roughness of Zn1-xMgxO epitaxy film is 2.3 nm. The photoluminescence emission energy is 3.603 eV and the FWHM is 41.4 meV. It implies the growth of high Mg concentration and high quality film was achieved. This study shows that the surface roughness and optical properties can be improved by optimizing the II/VI flux ratios, inserting low-temperature buffer layer and annealing process. The high quality ZnO and Zn1-xMgxO epilayers can be used to fabricate high quality ZnO/ZnMgO multiple quantum well structures.