本篇論文中，我們使用原子力式顯微鏡配合導電探針去量測蝕刻和非蝕刻的氮化鎵表面微觀的電流傳導特性，由於表面形貌和相對的電流分布可同時獲得，我們可去探討其兩者之間的關係。首先，我們觀察使用低溫MBE成長在MOCVD成長的氮化鎵表面，發現在六角形洞偏軸的斜面上，其導電能力較其他部分還高，接著在使用氫氧化鈉於室溫下蝕刻後，發現電流變的較蝕刻前均勻許多，因此推測原電流分布不均的現象有可能是氮的分布不均勻所造成。

　　再來我們使用ICP蝕刻獲得氮化鎵的奈米柱，其直徑約介於50奈米至200奈米間，不論由電特性或光的特性的量測，我們皆可觀察到由蝕刻所造成的表面效應。由導電的原子力式顯微鏡的量測結果，我們可發現電流均分布在離子轟擊所造成的蝕刻面，而在PL的光譜中，我們可發現由蝕刻所造成的施體-受體對(DAP)，而且我們亦發現，當對表面作奈米尺寸的蝕刻後，其光譜較蝕刻前還要好。

　In the thesis, we use conductive atomic force microscopy (C-AFM) to map out local current variations on etched and as-grown GaN films, focusing on the effect of off-axis facet planes on current conduction. First, in the samples grown by MBE on MOCVD templates, we investigated the off-axis planes of the hexagonal holes show a higher conductivity than surrounding areas. After NaOH room-temperature etching, samples show more uniform current distribution than before. It indicated the inhomogeneous current might be caused by the non-uniform distribution of nitrogen.

　Second, GaN nanopillars of diameter ranging from 50 nm to 200 nm were fabricated by ICP etching. Both by electrical and optical measurements, the surface effect which was caused by plasma-induced damage was found. In C-AFM results, current on the etching surface was detected, while other surface was not. In PL results, etching induced DAPs were found. By nanometer-size etching, better optical properties were also observed.

[1] H. Amano et al., Metalorganic vapor phase epitaxial growth of high quality GaN films using an AlN buffer layer, Appl. Phys. Lett. 48, 353 (1986).
[2] Shuji Nakamura and Takashi Mukai, High-quality InGaN films grown on GaN films,Jpn. J. Appl. Physics. 31, L1457, (1992).
[3] Shuji Nakamura et al., Novel metalorganic chemical vapor deposition system for GaN growth, Appl. Phys. Lett. 58, 2021 (1991).
[4] Shuji Nakamura et al., Hole compensation mechanism of p-type GaN films, Jpn. J. Appl. Physics. 31, 1258 (1992).
[5] S. Nakamura and G. Fasol, The Blue Laser Diode: GaN Based Light Emitters and Lasers (Springer, New York, 1997).
[6] B. Gil, Group III Nitride Semiconductor Compounds (Oxford Science, 1998).
[7] G. Binnig, H. Rohrer, C. Gerber, and E. Weibel, Surface Studies by Scanning Tunneling Microscopy, Phys. Rev. Lett. 49, 57 (1982).
[8] G. Binnig, H. Rohrer, C. Gerber, and E. Weibel, 7 × 7 Reconstruction of Si (111) Resolved in Real Space, Phys. Rev. Lett. 50, 120 (1983).
[9] G. Binnig, C. F. Quate, and C. Gerber, Atomic Force Microscope, Phys. Rev. Lett. 56, 930 (1986).
[10] Lander, J. J., Gobeli, G. W. , Morrison, J. (1963): J, Appl. Phys. 34, 2298.
[11] Bachmann, R. (1968): Phys. kondens. Materie 8, 31.
[12] Guichar, G. M., Sebenne, C., Garry, G., Balkanski, M. (1975): Le Vide 30, 97.
[13] Richter, E. (1963): Z. Naturforschung 18a, 39.
[14] Harrison, W. A. (1973): Phys. Rev. B8, 4487.
[15] M. Ali Omar, Elementary Solid State Physics, Addison-Wesley publishing company.
[16] Dawn A. Bonnell, Scanning Probe Microscopy and Spectroscopy, Wiley-VCH, p16, 2001.
[17] Y. Martin, C.C. Williams and H. K. Wickramadinghe, Jpn. J. Appl. Phys. 61, 4723(1987).
[18] F. J. Giessibl, Ch. Gerber, and G. Binnig, J. Vac. Sci. Technol. B 9, 984 (1991).
[19] P. K. Hansma, J. P. Cleveland, M. Radmacher, D. A. Walters, P. E. Hillner, M. Bezanilla, M. Fritz, D. Vie, and H. G. Hansma, Tapping mode atomic force microscopy in liquids, Appl. Phys. Lett. 64, 1738 (1994).
[20] R. E. Thomson and J. Moreland: Development of highly conductive cantilevers for atomic force microscopy point contact measurements, J. Vac. Sci. Technol. B 13 (3), 1123 (1995).
[21] A. Bietsch, M. A. Schneider, M. E. Welland, and B. Michel: Electrical testing of gold nanostructures by conducting atomic force microscopy, J. Vac. Sci. Technol. B 18 (3), 1160 (2000).
[22] K. T. Liu, T. Tezuka, S. Sugita, Y. Watari, Y. Horikoshi, Y. K Su, and S. J. Chang, Modulated beam growth method for MBE grown GaN layers, J. Cryst. Growth 263, 400 (2004).
[23] J. W. P. Hsu, M. J. Manfra, D. V. Lang, S. Richter, S. N. G. Chu, A. M. Sergent, R. N. Kleiman, L. N. Pfeiffer, and R. J. Molnar, Inhomogeneous spatial distribution of reverse bias leakage in GaN Schottky diodes, Appl. Phys. Lett. 78. 1685 (2001).
[24] J. W. P. Hsu, M. J. Manfra, R. J. Molnar, B. Heying, and J. S. Speck, Direct imaging of reverse-bias leakage through pure screw dislocations in GaN films grown by molecular beam epitaxy on GaN templates, Appl. Phys. Lett. 81, 79 (2002).
[25] J. W. P. Hsu, M. J. Manfra, S. N. G. Chu, C. H. Chen. L. N. Pfeiffer, and R. J. Molnar, Effect of growth stoichiometry on the electrical activity of screw dislocations in GaN films grown by molecular-beam epitaxy, Appl. Phys. Lett. 78, 3980 (2001).
[26] B. S. Simpkins, E. T. Yu, P. Waltereit, and J. S. Speck, Correlated scanning Kelvin probe and conductive atomic force microscopy studies of dislocations in gallium nitride, J. Appl. Phys. 94, 1448 (2003).
[27] U. Karrer, O. Ambacher, and M. Stutzmann, Influence of crystal polarity on the properties of Pt/GaN Schottky diodes, Appl. Phys. Lett. 77, 2012 (2000).
[28] B. Heying, R. Averbeck, L. F. Chen, E. Haus, H. Riechert, and J. S. Speck, Control of GaN surface morphologies using plasma-assisted molecular beam epitaxy, J. Appl. Phys. 88, 1855 (2000).
[29] D. Huang, P. Visconti, K. M. Jones, M. A. Reshchikov, F. Yun, A. A. Baski, T. King, and H. Morkoç, Dependence of GaN polarity on the parameters of the buffer layer grown by molecular beam epitaxy, Appl. Phys. Lett. 78, 4145 (2001).
[30] X. Q. Shen, T. Ide, S. H. Cho, M. Shimizu, S. Hara, and H. Okumura, Stability of N- and Ga-polarity GaN surfaces during the growth interruption studied by reflection high-energy electron diffraction, Appl. Phys. Lett. 77, 4013 (2000).
[31] A. R. Smith, R. M. Feenstra, D. W. Greve, M. S. Shin, M. Skowronski, J. Neugebauer, and J. E. Northrup, Determination of wurtzite GaN lattice polarity based on surface reconstruction, Appl. Phys. Lett. 72, 2114 (1998).
[32] Kenji Shiojima, Atomic force microscopy and transmission electron microscopy observations of KOH-etched GaN surfaces, J. Vac. Sci. Technol. B, Vol. 18, No. 1, 37 (2000).
[33] J. spradlin, S. Doğan, J. Xie, R. Molnar, A. A. Baski, and H. Morkoç, Investigation of forward and reverse current conduction in GaN films by conductive atomic force microscopy, Appl. Phys. Lett. 84, 4150 (2004).
[34] A. A. Pomarico, D. Huang, J. Dickinson, A. A. Baski, R. Cingolani, H. Morkoç, and R. Molnar, Current mapping of GaN films by conductive atomic force microscopy, Appl. Phys. Lett. 82, 1890 (2003).
[35] S. C. Jain, M. Willander, J. Narayan, and R. Van Overstraeten, III-nitrides: Growth, characterization, and properties, J. Appl. Phys. 87, 965 (2000).
[36] W. Gőtz, N. M. Johnson, C. Chen, H. Liu, C. Kuo, and W. Imler, Activation energies of Si donors in GaN, Appl. Phys. Lett. 68, 3144 (1996).
[37] J. J. Song and W. Shan, in Group III Nitride Semiconductor Compounds, edited by B. Gil (Clarendon, Oxford, 1998), pp. 182~241.
[38] S. Strite and H. Morkoç, J. Vac. Sci. Technol. B 10, 1237 (1992).
[39] S. J. Pearton, J. W. Lee, J. D. MacKenzie, C. R. Abernathy, and R. J. Shul, Dry etch damage in InN, InGaN, and InAlN, Appl. Phys. Lett. 67, 2329 (1995).
[40] F. Demangeot, J. Gleize, J. Frandon, M. A. Renucci, M. Kuball, D. Peyrade, L. Manin-Ferlazzo, Y. Chen, and N. Grandjean, Optical investigation of micrometer and nanometer-size individual GaN pillars fabricated by reactive ion etching, J. Appl. Phys. 91, 6520 (2002).
[41] P. Perlin et al., Phys. Rev. Lett. 75, 296 (1995).