New Physics: Sae Mulli (새물리)

Korean Physical Society (한국물리학회)
권호 표지
DOI QR코드

DOI QR Code

Influences of the Composition on Spectroscopic Characteristics of AlxGa1-xN Thin Films

AlxGa1-xN 박막의 조성이 분광학적 특성에 미치는 영향

  • Kim, Dae Jung (School of Basic Sciences, Hanbat National University) ;
  • Kim, Bong Jin (School of Basic Sciences, Hanbat National University) ;
  • Kim, Duk Hyeon (School of Basic Sciences, Hanbat National University) ;
  • Lee, Jong Won (Department of Advaned Materials Engineering, Hanbat National University)
  • Received : 2018.09.07
  • Accepted : 2018.10.30
  • Published : 2018.12.31
⟨ Previous Next ⟩

Abstract

In this study, $Al_xGa_{1-x}N$ films were grown on (0001) sapphire substrates by using metal-organic chemical vapor deposition (MOCVD). The crystallinity of the grown films was examined with X-ray diffraction (XRD) patterns. The surfaces and the chemical properties of the $Al_xGa_{1-x}N$ films were investigated using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. The optical properties of the $Al_xGa_{1-x}N$ film were studied in a wide photon energy range between 2.0 ~ 8.7 eV by using spectroscopic ellipsometry (SE) at room temperature. The data obtained by using SE were analyzed to find the critical points of the pseudodielectric function spectra, $<{\varepsilon}(E)>=<{\varepsilon}_1(E)>+i<{\varepsilon}_2(E)>$. In addition, the second derivative spectra, $d^2<{\varepsilon}(E)>/dE^2$, of the pseudodielectric function for the $Al_xGa_{1-x}N$ films were numerically calculated to determine the critical points (CPs), such as the $E_0$, $E_1$, and $E_2$ structure. For the four samples (x = 0.18, 0.21, 0.25, 0.29) between a composition of x = 0.18 and x = 0.29, changes in the critical points (blue-shifts) with increasing Al composition at 300 K for the $Al_xGa_{1-x}N$ film were observed via ellipsometric measurements for the first time.

본 연구에서는 $Al_xGa_{1-x}N$ 박막을 유기금속 화학증착법(metal organic chemical vapor deposition, MOCVD) 을 이용하여 사파이어 (0001) 기판 위에 성장하였다. 성장된 박막의 결정구조를 조사하기 위하여 엑스선 회절 (X-ray diffraction, XRD) 패턴을 이용하였고, 박막의 표면 상태를 관찰하기 위하여 원자간력 현미경(atomic force microscopy, AFM)을 사용하였다. 또한 박막의 화학성분과 결합상태는 엑스선 광전자 분광분석기(X- ray photoelectron spectroscopy, XPS)를 이용하여 분석하였다. 박막의 광학적 특성인 유사유전함수는 분광학적 타원편광분석법(spectroscopic ellipsometry, SE)을 사용하여 실온에서 2.0 ~ 8.7 eV 포톤에너지 범위에서 측정되었다. 타원편광분석법으로 조사된 데이터들을 통해 얻은 유사유전함수 스펙트럼 $<{\varepsilon}(E)>=<{\varepsilon}_1(E)>+i<{\varepsilon}_2(E)>$에 나타난 $E_0$, $E_1$, 그리고 $E_2$ 와 같은 임계점 구조에 대하여 연구하였고, 각각의 임계점 피크들은 획득된 유사유전함수의 데이터를 이차 미분한 이계도함수 $d^2<{\varepsilon}(E)>/dE^2$ 를 이용하여 구하였다. 특히, x = 0.18과 x = 0.29 사이에 위치한 샘플(x = 0.18, 0.21, 0.25, 0.29)들은 Al의 조성이 증가함에 따라 임계점 피크들이 변화(blue-shift)한다는 것을 관측하였고, 이를 다른 문헌들과 비교 분석하였다.

Keywords

References

  1. S. Nakamura and G. Fasol, The Blue Laser Diode (Springer-Verlag, New York, 1997).
  2. J. Kwak, J. Lim, M. Park, S. Lee and K. Char et al., Nano Lett. 15, 3793 (2015). https://doi.org/10.1021/acs.nanolett.5b00392
  3. M. A. Khan, M. S. Shur, J. N. Kuzunia, Q. Chin and J. Burm et al., Appl. Phys. Lett. 66, 1083 (1995). https://doi.org/10.1063/1.113579
  4. Z. Wang, J. Cao, R. Sun, F. Wang and Y. Yao, Superlattices Microstruct. 120, 753 (2018). https://doi.org/10.1016/j.spmi.2018.06.045
  5. D. Fritsch, H. Schmidt and M. Grundmann, Phys. Rev. B 67, 235205 (2003). https://doi.org/10.1103/PhysRevB.67.235205
  6. F. Fedler, R. J. Hauenstein, H. Klausing, D. Mistele and O. Semchinova et al., J. Cryst. Growth 241, 535 (2002). https://doi.org/10.1016/S0022-0248(02)01324-6
  7. N. H. Zhang, X. L. Wang, Y. P. Zeng, H. L. Xiao and J. X. Wang et al., J. Cryst. Growth 280, 346 (2005). https://doi.org/10.1016/j.jcrysgro.2005.03.080
  8. H. Sasaki, S. Kato, T. Matsuda, Y. Sato and M. Iwami et al., J. Cryst. Growth 298, 305 (2007). https://doi.org/10.1016/j.jcrysgro.2006.10.058
  9. O. Klein, J. Biskupek, K. Forghani, F. Scholz and U. Kaiser, J. Cryst. Growth 324, 63 (2011). https://doi.org/10.1016/j.jcrysgro.2011.03.050
  10. S. Ruffenach-Clur, O. Briot, J. L. Rouviere, B. Gil and R. L. Aulombard, Mater. Sci. Eng. B 50, 219 (1997). https://doi.org/10.1016/S0921-5107(97)00166-9
  11. B. Rezaei, A. Asgari and M. Kalafi, Physica B 371, 107 (2006). https://doi.org/10.1016/j.physb.2005.10.003
  12. M. Stutzmann, O. Ambacher, A. Cros, M. S. Brandt and H. Angerer et al., Mater. Sci. Eng. B 50, 212 (1997). https://doi.org/10.1016/S0921-5107(97)00165-7
  13. T. Wethkamp, K. Wilmers, N. Esser, W. Richter and O. Ambacher et al., Thin Solid Films 313-314, 745 (1998). https://doi.org/10.1016/S0040-6090(97)00990-5
  14. R. S. Balmer, C. Pickering, A. M. Kier, J. C. H. Birbeck and M. Saker et al., J. Cryst. Growth 230, 361 (2001). https://doi.org/10.1016/S0022-0248(01)01254-4
  15. Y. Liu, Q. Li, L. Wan, B. Kucukgok and E. Ghafari et al., Appl. Surf. Sci. 421, 389 (2017). https://doi.org/10.1016/j.apsusc.2017.01.309
  16. T. Miyazaki, T. Fujimaki, S. Adachi and K. Ohtsuka, J. Appl. Phys. 89, 8316 (2001). https://doi.org/10.1063/1.1368393
  17. T. Kawashima, H. Yoshikawa, S. Adachi, S. Fuke and K. Ohtsuka, J. Appl. Phys. 82, 3528 (1997). https://doi.org/10.1063/1.365671
  18. N. V. Edwards, S. D. Yoo, M. D. Bremser, M. N. Horton and N. R. Perkins et al., Thin Solid Films 313-314, 187 (1998). https://doi.org/10.1016/S0040-6090(97)00815-8
  19. W. Luo, X. Wang, H. Xiao, C. Wang and J. Ran et al., Microelectronics J. 39, 1108 (2008). https://doi.org/10.1016/j.mejo.2008.01.083
  20. A. Hussein, Z. Hassan, S. Thahab, S. Ng and H. Hassan et al., Appl. Surf. Sci. 257, 4159 (2011). https://doi.org/10.1016/j.apsusc.2010.11.189
  21. A. Hussein, Z. Hassan, S. Thahab, A. Hassan and M. Abid et al., Physica B 406, 1267 (2011). https://doi.org/10.1016/j.physb.2011.01.014
  22. A. Salokatve and M. Hovinen, J. Appl. Phys. 67, 3378 (1990). https://doi.org/10.1063/1.345381
  23. R. Sohal, P. Dudek and O. Hilt, Appl. Surf. Sci. 256, 2210 (2010). https://doi.org/10.1016/j.apsusc.2009.09.075
  24. X. L. Wang, D. G. Zhao, J. Chen, X. Y. Li and H. M. Gong et al., Appl. Surf. Sci. 252, 8706 (2006). https://doi.org/10.1016/j.apsusc.2005.12.057
  25. Y. Zhong, Y. Zhou, H. Gao, S. Dai and J. He et al., Appl. Surf. Sci. 420, 817 (2017). https://doi.org/10.1016/j.apsusc.2017.05.185
  26. J. W. Do, H. W. Jung, M. J. Shin, H. K. Ahn and H. kim et al., Thin Solid Films 628, 31 (2017). https://doi.org/10.1016/j.tsf.2017.02.053
  27. M. Cardona and D. L. Greenaway, Phys. Rev. 133, A1685 (1964). https://doi.org/10.1103/PhysRev.133.A1685
  28. S. Logothetidis, J. Petalas, M. Cardona and T. D. Moustakas, Phys. Rev. B 50, 18017 (1994). https://doi.org/10.1103/PhysRevB.50.18017
  29. K. Miwa and A. Fukumoto, Phys. Rev. B 48, 7897 (1993). https://doi.org/10.1103/PhysRevB.48.7897
  30. C. S. Cook, S. Zollner, M. R. Bauer, P. Aella and J. Kouvetakis et al., Thin Solid Films 455-456, 217 (2004). https://doi.org/10.1016/j.tsf.2003.11.277
  31. L. Vina, S. Logothetidis and M. Cardona, Phys. Rev. B 30, 1979 (1984). https://doi.org/10.1103/PhysRevB.30.1979
  32. C. Buchheim, R. Goldhahn, M. Rakel, C. Cobet and N. Esser et al., Phys. Status Solidi B 242, 2610 (2005). https://doi.org/10.1002/pssb.200541265