利用原子層沉積技術成長p型氧化鋅之研究

本論文利用原子層沉積技術(Atomic Layer Deposition, ALD)成長高品質氧化鋅(Zinc Oxide, ZnO)，並利用不同的摻雜(Doping)技術將雜質(Impurities)加入ZnO薄膜中，再加上後續的熱退火(Post-annealing)以製作p型之ZnO。首先，本研究利用ALD技術在(0001)Al2O3基板上成長重度摻雜(Heavily Doping)達10%的氧化鋅鋁(ZnO:Al)，以分散摻雜(Distributed Doping)的方式將鋁加入ZnO薄膜中。我們發現在退火環境氣氛(Ambient Gas)為N2:O2=1:1與退火溫度(Annealing Temperature)達800℃以上時，ZnO的電子濃度有顯著下降的趨勢，約比未退火前下降了三到四個數量級，並在低溫(14K)的光激發光(Photoluminescence, PL)量測中觀測到受子能階(Acceptor Level)的訊號，顯示電子濃度的下降是由於重度摻雜鋁之ZnO內形成受子能階所導致。目前廣泛認為，摻雜V族元素進入ZnO中去填補氧空缺(Oxygen Vacancy, VO)，產生受子能階以提供電洞(Hole)，是製作p型ZnO相當被看好的一種方式。本研究利用ALD技術在半絕緣(Semi-insulating)之(100)砷化鎵(Gallium Arsenic, GaAs)基板上成長ZnO，再進一步地使用高溫爐做熱擴散(Thermal Diffusion)，將砷擴散進入ZnO中形成如AsZn-2VZn等複合物(Complex)，作為受子能階以提供電洞。接著以快速熱退火(Rapid Thermal Annealing, RTA)的方式修補晶格缺陷與活化受子能階，製作出品質良好的p型摻雜砷之ZnO。由霍爾效應(Hall Effect)量測得知其電洞濃度為1017~1019cm-3，載子遷移率(Mobility)在100~101 cm2V-1s-1這個範圍，並在低溫PL量測也觀測到位於約3.32eV明顯的受子能階之訊號。最後，本研究利用離子佈植(Ion Implantation)的方式，將V族元素如氮(Nitrogen, N)、磷(Phosphorous, P)及砷摻雜於ZnO薄膜中，並使用後續的熱退火修補因離子束破壞所造成的缺陷以及活化受子能階。我們發現以能量70keV，劑量5x1015cm-2將砷打入ZnO薄膜中，再以溫度為750℃，全氧氣的環境下退火兩小時，可得到電性良好的p型摻雜砷之ZnO。霍爾效應量測顯示其電洞濃度約1016~1017cm-3，而低溫PL量測也可觀測得受子能階的訊號，可作為p型 ZnO的佐證。

關鍵字

原子層沉積技術；氧化鋅；熱擴散；離子佈植； p型

並列摘要

In this thesis, p-type zinc oxide (ZnO) was developed by atomic layer deposition (ALD), coupled with the introduction of impurities via various doping techniques and post-deposition annealing. First of all, ZnO thin films were deposited on (0001) sapphire substates by atomic layer deposition with Al doping percentage up to 10%. The Al was incorporated into ZnO thin films by distributed layered doping. After the post-annealing at the temperatures greater than 800℃ in ambient gas of N2:O2=1:1, the Hall effect measurement indicated that the electron concentration in ZnO decreased about 3~4 orders of magnitude. Moreover, the low-temperature photoluminescence (PL) spectrum at 14K showed the spectral peak corresponding to the acceptor level, suggesting that the decrease of electron concentration was caused by the presence of the acceptors in the heavily Al-doped ZnO. Generally speaking, incorporating group-V impurities such as N, P, As, Sb as dopants into ZnO is regarded as a promising method to fabricate p-type ZnO. As group-V elements occupy oxygen vacancies, they will act as acceptor states and thus contribute holes in ZnO. In the second topic of this thesis, ZnO thin films were grown on semi-insulating, undoped (100) GaAs substrate by ALD. Then the ZnO thin films were treated by thermal diffusion using furnace. The As atoms diffused from GaAs into ZnO and the complex like AsZn-2VZn may be formed to act as the acceptor levels. Afterwards, the samples were annealed by rapid thermal annealing (RTA) to eliminate the defects and activate the acceptor states. Hall Effect measurement showed that the hole concentration was in the range of 1017~1019 cm-3, and carrie mobility was between 100 and 101 cm2V-1s-1. The low temperature PL measurement revealed the spectral peak at 3.32eV associated with the acceptor bound exciton. Finally, impurities such as N, P, and As were doped into ZnO thin films via ion implantation. Post-implantation annealing was applied to eliminate the defects and damages cause by the ion beams and activate the acceptor levels. High-quality p-type As-doped ZnO was obtained by ion implantation with energy of 70keV, dose of 5x1015cm-2, and post-annealing at 750℃ in oxygen ambient gas for 2 hours. Hall Effect measurement revealed that the hole concentration was about 1016~1017cm-3. The acceptor bound exciton was also observed in the low temperature PL spectrum , indicating the p-type characteristics of ZnO.

並列關鍵字

Atomic Layer Deposition ； ZnO ； Thermal Diffusion ； Ion Implantation ； p-type

參考文獻

[1] C.H. Park, S.B. Zhang, S.-H. Wei, “Origin of p-type doping difficulty in ZnO: The impurity perspective”, Phys. Rev. B 66 073202 (2002)

[2] E.C. Lee, Y.-S. Kim, Y.-G. Jin, K.H. Chang, “Compensation mechanism for N acceptors in ZnO”, Phys. Rev. B. 64 085120 (2002)

[3] M. Ritala and M. Leskela, “Atomic layer epitaxy—a valuable tool for nanotechnology?”, Nanotechnology 10 19 (1999)

[4] L. Niinistö*, J. Päiväsaari, J. Niinistö, M. Putkonen, and M. Nieminen, “Advanced electronic and optoelectronic materials by Atomic Layer Deposition: An overview with special emphasis on recent progress in processing of high-k dielectrics and other oxide materials” phys. stat. sol. (a) 201, 1443–1452 (2004)

[5] S. Y. Pung, K. L. Choy, X. G. Hou, “Preferential growth of ZnO thin films by the atomic layer deposition technique” , Nanotechnology 19 (2008)

國際替代計量

利用原子層沉積技術成長p型氧化鋅之研究

全文下載

主題瀏覽