在矽基板上成長三族氮化物之磊晶及物性研究

Abstract

本論文利用分子束磊晶法在矽基板上成長氮化鎵、氮化銦奈米柱與銦極性及氮極性的氮化銦薄膜。利用X光繞射、光激螢光光譜及拉曼光譜等實驗來研究其物理特性。 於利用成長的溫度和氮/鎵(銦)比例控制氮化鎵(銦)奈米柱的高寬比。發現在高度氮富含的條件下，氮化鎵(銦)奈米柱有較大的高寬比。以X光繞射與拉曼光譜的量測證明每一奈米柱皆為無應力之單晶結構。再利用氮化鎵奈米柱為緩衝層在矽基板上成長氮化鎵薄膜。發現當氮化鎵奈米柱的直徑小於80奈米時可成長出無應力的氮化鎵薄膜。另一方面也利用氮化銦奈米柱為緩衝層在矽基板上成長氮化銦薄膜，但因氮化銦奈米柱與矽基板間較弱的附著力，使氮化銦薄膜與矽基板產生剝離的現象。而從低溫光激螢光光譜的量測結果發現，相較於氮化銦薄膜成長在氮化鋁緩衝層上，其發光位置可由0.83電子伏特紅移至0.75電子伏特，螢光光譜的半高寬值可由150毫電子伏特降為110毫電子伏特。結果證明相較於氮化鋁緩衝層，在矽基板上以氮化銦奈米柱為緩衝層能有效改善氮化銦薄膜的品質。此外，也利用改變氮化鋁緩衝層與矽基板間鋁原子層的厚度，成功地控制氮化銦薄膜的極性。當鋁預沉積原子層的厚度大於一個原子層時，氮化銦薄膜的極性由氮極性轉為銦極性。利用化學溶液蝕刻法來判斷氮化銦薄膜的極性，經過化學溶液蝕刻後，氮極性的氮化銦薄膜表面變得粗糙且出現金字塔型的結構，銦極性的氮化銦薄膜表面不受影響。

In this dissertation, the growth of GaN nano-rods, InN nano-rods, In-polar and N-polar InN films on Si(111) substrate by molecular beam epitaxy (MBE) were studied. The x-ray diffraction (XRD), photoluminescence (PL) and Raman scattering were used to investigate the physical properties. The morphology of GaN (InN) nano-rods can be manipulated by the control of N/Ga (In) ratio and growth temperature. From slightly N-rich condition to highly N-rich condition, the aspect ratio of III-nitride nano-rods increases. The results of XRD and Raman scattering measurements, show that III-nitride nano-rods were strain-free single crystals. Using GaN nano-rods as buffer layer, strain-free GaN film on Si substrate is realized. It is clearly demonstrated that the critical diameter of GaN nano-rods is around 80 nm for the overgrowth of strain-free GaN. In the case of InN film overgrowth on InN nano-rods, film delimitation and cracking occurs during growth was observed. It is due to the poor adhesion between the rod and the Si substrate. Compare to the InN film grown on AlN/Si(111) substrate, low-temperature PL measurement shows that the emission peak energy of InN red shifts from 0.83 eV to 0.75 eV, and the full width at half maximum (FWHM) reduces from 150 meV to 110 meV. It implies that the InN film quality has been greatly improved. In addition, the lattice polarity of InN can be controlled by the thickness of initial Al-layer that was deposited prior to AlN buffer layer. A change from N-polar to In-polar was observed when Al-layer exceeded one monolayer. The lattice polarity of InN was determined by chemical wet etching method. In the case of N-polar InN, the surface became rough and pyramids after etching. In contrast, In-polar InN remained smooth surface.