摘 要 本實驗是在p型氮化鎵中佈植矽離子，經由氮氣環境下的快速熱退火處理而形成矽離子佈植試片。X-Ray布拉格繞射結果顯示，即使經由1150oC, 60秒快速熱退火處理，仍然無法將結構完全修復。藉由改變離子佈植及熱退火的條件可以將試片的電性由p型(~3´1017cm-3)轉變為n型(2´1017cm-3~2´1019cm-3)。本實驗發現矽原子在典型的矽離子佈植試片中，其活化能(~10 meV以下)比磊晶成長的矽摻雜試片(~15 meV以下)低，且多了一個深層能階(~60 meV)的施體。在光激發光譜的分析中，觀察到一個372nm峰值，它可能是由離子佈植所造成的結構破壞而引發的；另外，還觀察到一個525nm峰值，它可能源自跟磊晶成長式的矽摻雜n型氮化鎵所具有之黃光峰值一樣。 矽離子佈植式p-n二極體的特性分析中，在小的順向操作偏壓(Vj<2V)時，除了單純的複合電流與擴散電流之外，還存在一些由缺陷所造成的額外傳導電流，而這些缺陷的來源有可能是成長時的空缺或錯位，以及離子佈植所造成的結構破壞。在電激發光譜的分析中，觀察到一個430nm峰值，它可能是來自於和鎂有關的受體和未知施體之間的躍遷。另一方面，矽離子佈植式p-n二極體應用在逆向偏壓的操作範圍時，可以當作一個紫外光光檢測器。當外加的逆向壓在1V時，暗電流是50 nA/cm2，而當外加的逆向壓在3V時，暗電流是1.5 A/cm2。這個光檢測器的截止波長大約是365 nm(光響應強度約為 0.33 mA/W)，且對紫外光(~365 nm)和可見光(~500 nm)的鑑別度可達260倍。 Abstract Si ion implantation into p-type GaN followed by rapid thermal annealing (RTA) in N2 has been performed. X-ray diffraction analyses indicated that ion-implanted damage remains even with 1150oC, 60sec RTA. By varying implantation and post-implantation annealing conditions, we could convert carrier concentration from p-type 3´1017cm-3 into n-type 2´1017cm-3~2´1019cm-3. It was found that typical activation energies of Si implants in p-GaN are lower than 10 meV Such activation energies are smaller than those observed from epitaxially grown Si-doped GaN films (~15meV). A deep donor level with activation energy of 60meV was also found from some samples. Photoluminescence (PL) studies show that the peak appears at 372nm might be related to implantation-induced defects. A green emission band was observed from Si-implanted GaN. This green emission may be related to the yellow band observed for the epitaxially grown Si-doped GaN. Characterizations of GaN n+-p junction diodes formed by Si implantation into p-GaN were also performed by using various techniques including current-voltage(I-V) measurements and electroluminescence(EL) spectroscopy. The current-voltage characteristics at low forward bias region (Vj<2 V) are measured. It might be interpreted as the results are governed by a trap-assisted generation-recombination mechanism rather than a simple recombination current. In addition to the grow-in defects including vacancies(VGa VN) and dislocation, ion implantation would further induce more defects or unrecoverable structural damage in the implanted layers, which these are the source of possible trap-assisted generation-recombination centers, and affect significantly the characteristics of optical and electrical properties. For EL measurements, a blue band emission around 430 nm was observed, which can be attributed to a Mg-related donor-to-acceptor transition. On the other hand, for the application in visible blind UV detector, the Si-implanted planar GaN p-n diodes are also a potential candidate. The current density measured under dark condition is around 1.5 mA/cm2 and 50 nA/cm2 at a reverse bias of 3 V and 1V, respectively. Spectra response measurements revealed a cut-off wavelength of about 365 nm and a peak responsivity of around 0.33 mA/W at 365 nm. In addition, the photodiodes showed a typical visible rejection ratio, which divides the values of the responsivity at 365 nm and at 500 nm, of around 260.
