以不同介面磊晶方式調控氮化鋁鎵／氮化鎵異質結構之電特性分析

Abstract

本論文使用分子束磊晶系統成長氮化鎵薄膜，氮化鋁鎵薄膜及氮化鋁鎵/氮化鎵二維電子氣結構。氮化鎵薄膜方面利用不同的長晶參數，去觀察氮化鎵薄膜的平整度、光譜變化。在氮化鋁鎵薄膜部分，利用不同的鋁鎵流量比、基板溫度去成長鋁含量不同且高品質的氮化鋁鎵。最後成長氮化鎵/氮化鋁鎵二維電子氣結構，並改變不同的介面磊晶方式，去觀察其對改善遷移率、片電阻和載子濃度的影響。 在氮化鎵薄膜的研究中，在鎵元素流量為1.20× 10-7 torr， N2流量為0.9 SCCM，基板溫度為710 ˚C時，有較好的平整度。氮化鋁鎵薄膜方面，已成功長出鋁含量4%~25%的高品質氮化鋁鎵。在氮化鋁鎵/氮化鎵二維電子氣結構中，本論文在介面處理方式使用成長氮化鋁鎵/氮化鎵超晶格(Superlattice)的方式，成功長出低片電阻的二維電子氣結構，其值為599.6 𝜴/sq，遷移率和載子濃度分別為732.2 cm2/ V-s和1.42×1013 cm-2。

In this thesis, GaN thin films, AlxGa1-xN thin films and AlxGa1-xN/GaN two dimensional electron gas (2DEG) structures were grown by molecular beam epitaxy (MBE). Surface morphology and optical properties of GaN thin films were observed to study the effect of different epitaxy parameters. Different Al compositions of high quality AlxGa1-xN thin films were controlled by varying the Al/Ga flux ratios and substrate temperatures. Effects of the interfacial epitaxy on the electrical properties, mobility, sheet resistance and sheet carrier concentration, of AlxGa1-xN/GaN 2DEG were studied. In the study of GaN thin films, the best surface roughness was achieved by using Ga flux of 1.20× 10-7 torr, N2 Plasma flux of 0.9 SCCM, and substrate temperature of 710 oC. High quality AlxGa1-xN thin films of x=4%~25% were successfully grown. AlxGa1-xN/GaN 2DEG structure of low sheet resistance of 599.6 𝜴/sq was also successfully grown by using super-lattice interfacial epitaxy. The mobility of 732.2 cm2/ V-s and sheet carrier concentration of 1.42×1013 cm-2 were obtained.