III-V族氮化物半導體在過去二十年間快速發展，已大量應用於各種消費性產品與資訊設備。在III-V族氮化物中，氮化硼(BN)具有許多優越的特性，例如h-BN (hexagonal-boron nitride) 的能隙高達6 eV，激子束縛能高達130 meV，而鎂在h-BN的電洞活化能低至30 meV，也有小的電洞等效質量，這表示h-BN不但具有高崩潰電場，亦較AlN更易成為具有高導電率的p-型半導體，這在深紫外光發光二極體與高功率元件的應用非常有利。BN雖然極具應用潛力，但是若能與其他氮化物形成合金或異質結構，例如與較成熟的氮化鎵系列材料結合，將可提供更大的自由度來調控能隙與晶格常數，其應用範圍與創新的機會將更為豐富。儘管含硼氮化物理論上具有多項潛力，但是目前為止都尚未實現。關鍵問題就在於材料製備技術尚未成熟，就連理論計算所依據的參數是否正確亦值得深究。要充分利用含硼氮化物之優點，磊晶技術必須要大幅進步。目前BAlGaInN材料之相關研究在國際上尚屬起步，在國內則尚未啟動，此計畫擬以三年為期，探討有機金屬化學蒸氣沉積法(MOCVD)磊晶成長技術，並針對BN以及其與AlGaInN形成的合金與異質結構進行系統性的研究。第一年將聚焦於BGaN及BAlN三元化合物的磊晶成長與基本材料特性分析；第二年將著重BAlGaInN異質結構之成長，以探討硼含量對自發極化係數的影響以及各種異質結構的能隙差參數(energy band offsets)；第三年的研究重點則在含硼氮化物的元件應用，將探討以含硼氮化物作為GaN HEMT的緩衝層、位障層與鈍化層之功效。預期可豐富此材料之資料庫，並開拓一個新的研究與應用領域。 ;Technology advancement of III-nitride semiconductors has been very impressive in the last 20 years as evidenced by its wide adoption in consumer products as well as equipment in information and communication technology sector. Among the III-nitrides, boron nitride (BN) is a material with several merits for future applications. For instance, h-BN has bandgap as large as 6 eV, it has an exciton binding energy as high as 130 meV. The acceptor activation energy of Mg in h-BN is reported to be as small as 30 meV with a small hole effective mass. This means h-BN has a high breakdown field and can be a much more conductive p-type semiconductor than its AlN counterpart. These are very essential for applications in deep ultra-violet light emitting diodes and high power devices. Given the aforementioned advantages of h-BN, it would be even more desirable if BN could be combined with more well-developed GaN-based materials to form alloys and heterostructures so that a greater flexibility of material design is offered to pave the way to more innovative applications. While all the positive aspects predicted theoretically for B containing nitrides, none of them have been realized so far. This is basically due to the limited advancement of material preparation technology. Without high quality materials, the material parameters used for predicting all these positive potentials might also be in question. It is obvious that epitaxial growth technology must be greatly improved to realize these potentials. As the development of BAlGaInN material is still in its infant stage globally and no such activity is found in Taiwan, a three-year plan is proposed to develop metal-organic chemical vapor deposition (MOCVD) epitaxy technology of this novel material and systematically investigate its fundamental properties. The first year will be focused on the growth BGaN and BAlN ternary compounds and investigation of their fundamental properties; the second year will be devoted to the growth of BAlGaInN heterostructures to investigate the dependence of B content on spontaneous polarization constant and their energy band offsets; and the their year will be used to explore the possibilities of applying these B-containing materials to GaN-based high electron mobility transistors (HEMTs) as a buffer layer, barrier layer as well as a passivation layer. This work is expected to enrich the data base of this material system and open a new area of research.
