| 摘要: | III族氮化物材料，包括氮化鎵（GaN）、氮化鋁（AlN）、氮化銦（InN）及其合金，已經徹底革新了現代化合物半導體技術，推動了光電和高功率電子設備的突破性發展。基於GaN的LED和雷射構成了固態照明和光學技術的基礎，而GaN高電子遷移率電晶體（HEMT）在電信和電力電子領域中發揮了重要作用，以其卓越的效率和性能備受青睞。然而，儘管具有巨大潛力，III族氮化物材料的磊晶生長仍面臨顯著挑戰，尤其是由於缺乏原生基板。傳統的磊晶方法通常依賴藍寶石、矽（Si）或碳化矽（SiC）等異質基板，而這些基板與III族氮化物存在晶格和熱膨脹係數失配，從而引入應變和缺陷。
III族氮化物材料的磊晶生長技術中，有機金屬化學蒸氣沉積（MOCVD）技術因其具可擴展性、材料組合彈性以及成長參數的精確控制而成為關鍵的製造技術。本論文首先研究了二維材料氮化硼（sp2-BN）的有機金屬化學蒸氣沉積晶圓級藍寶石和矽基板上成長，通過多種實驗技術對所成長的氮化硼材料進行了全面的分析。研究發現，在藍寶石表面形成鋁氧氮化物（AlNxOy）層是生長二維BN材料的必要步驟，而在矽基板上，以脈衝流模式成長能夠有效促進二維BN的成長，儘管其晶格失配高達約34%。
隨後，我們探討了二維BN作為III族氮化物生長中介層的作用。此方法面臨著III族氮化物成核和自剝離的挑戰，這主要源於二維BN的表面無懸鍵可以和外來原子鍵結。我們克服了這些挑戰，並提出了一個自剝離機制模型，其中界面結合能是控制自剝離過程的關鍵。我們成功地展示了使用較薄的二維BN中介層實現材料品質改進和可控的磊晶剝離（ELO）情形，並且得以保持剝離後之多量子井結構的發光性能，無任何退化狀況。
本研究進一步探討了二維BN作為中介層在熱性能優越的多晶氮化鋁（poly-AlN）基板上生長III族氮化物的可行性和潛力。並以結構和光學分析方法，包括X射線繞射（XRD）、電子背向散射繞射（EBSD）和光激發光光譜，證實了使用BN中介層的poly-AlN模板上可以實現了III族氮化物的單晶生長。密度泛函理論（DFT）計算結果顯示，實現poly-AlN基板上磊晶III族氮化物需要優化h-BN層的厚度，以抑制來自多晶基板的遠程相互作用。
此外，本研究還聚焦於硼基sp3相III族氮化物合金的磊晶成長與特性分析。通過在III族氮化物中引入硼，可形成三元和四元B(Al, Ga, In)合金，為III族氮化物提供更大的帶隙調節能力和晶格匹配選項。本研究有系統地研究了成長參數對B(Al, Ga)N合金結構特性的影響，成功地實現了0%-6%硼含量的三元BGaN合金和0%-13%硼含量的BAlN合金。進一步研究了B(Al, Ga)N與傳統III族氮化物材料的異質結帶隙對齊情況。結果顯示，B(Al, Ga)N異質接面可以實現第I型和第II型帶隙對齊，我們也以p-d軌道耦合理論闡述其價帶偏移VBO的趨勢 。
總體而言，本研究探討了sp2相BN在實現矽基板上的III族氮化物凡德瓦磊晶。此外，還研究了Wurtzite 相B(Al, Ga)N合金，以拓展III族氮化物材料的功能範圍及其元件應用潛力。
;III-nitride materials, including gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), and their alloys, have revolutionized modern compound semiconductor technology, driving breakthroughs in optoelectronics and high-power electronic devices. GaN-based LEDs and lasers form the foundation of solid-state lighting and optical technologies, while GaN high-electron-mobility transistors (HEMTs) play a crucial role in telecommunications and power electronics, offering exceptional efficiency and performance. Despite their potential, the growth of III-nitride materials presents significant challenges, particularly due to the lack of native substrates. Conventional epitaxy methods often rely on heteroepitaxy on substrates such as sapphire, silicon (Si), or silicon carbide (SiC), all of which exhibit lattice and thermal mismatches with III-nitride materials, introducing strain and defects. Conventional approaches, such as low-temperature nucleation layers, graded buffer layers, and superlattice structures, have achieved partial success but remain limited in their ability to produce strain and defect-free, scalable III-nitride layers. These limitations have motivated the exploration of alternative growth approach, mediated by two-dimensional (2D) materials by leveraging the weak interlayer bonding of 2D materials.
A key manufacturing process for growth of these III-nitride materials remained the metal-organic chemical vapor deposition (MOCVD), as of its scalable growth, integration of various materials and accurate control over the growth parameters. This thesis first explores the wafer-scale growth of 2D material boron nitride (sp2-BN), itself a potential candidate in III-nitride materials on cost-effective sapphire and silicon substrates utilizing the advantageous MOCVD approach. A comprehensive characterization of the grown BN material was undertaken using various experimental techniques. A formation of an aluminium oxynitride (AlNxOy) layer on the surface of sapphire is found to be a necessary step for the growth of 2D BN material on sapphire, whereas, for Si substrates, the pulsed-flow mode MOCVD growth method effectively facilitates the growth of 2D BN on Si, despite the substantial lattice mismatch of ~34%.
Subsequently, 2D-BN′s role as a mediator for III-nitride growth is explored. This growth method presents challenges such as nucleation and self-delamination of III-nitrides, arising from 2D-BN’s dangling bond-free surface and weak interface bonding. These challenges are addressed, and a model for the self-exfoliation mechanism is proposed, where the interface binding energy plays a role in controlling the self-exfoliation process. Structural improvements and controlled epitaxial lift-off (ELO) were successfully demonstrated with thinner h-BN layers, enabling the realization of multiple quantum-well structures that retained their emission properties post-ELO without degradation.
This study further highlights the feasibility and potential of 2D-BN as a mediator for the growth of III-nitrides on thermally superior polycrystalline aluminum nitride (poly-AlN) substrates. Structural and optical analyses, including X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and photoluminescence spectroscopy, confirm the successful single-crystalline growth of III-nitrides on BN-mediated poly-AlN templates. Density functional theory (DFT) calculations indicate that achieving crystalline III-nitride growth on poly-AlN substrates requires an optimized h-BN layer sufficiently thick to suppress remote interactions from the polycrystalline substrate.
Another focus of this study is the growth and characterization of boron-based sp3-phase III-nitride alloys. Incorporating boron into III-nitrides enables the formation of ternary and quaternary B(Al, Ga, In) alloys, offering more bandgap tunability and lattice-matching options in III-nitrides. This study systematically investigates the growth parameters and their impact on the structural properties of B(Al, Ga)N alloys. Ternary BGaN alloys with 0%–6% boron composition and BAlN alloys with 0%–13% boron compositions are realized. The band alignment studies of B(Al, Ga)N heterojunctions with conventional III-nitride materials are further investigated. Both type-I and type-II band alignments are possible with B(Al, Ga)N heterojunctions, and the valence band offset (VBO) of these heterojunctions is compared and discussed in the context of p–d orbital coupling.
Overall, this work investigates the applicability of the sp2 phase BN in enabling the van der Waals growth of III-nitrides, particularly on Si substrates. Additionally, it explores the sp3 phase of B(Al, Ga)N alloys to expand the functional scope of III-nitride materials alongside with boron. |
