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Micro and nano analysis of 0.2 mm Ti/Al/Ni/Au ohmic contact to AlGaN/GaN

Micro and nano analysis of 0.2 mm Ti/Al/Ni/Au ohmic contact to AlGaN/GaN. A. Fontsere`,1,a) A. Pe´rez-Toma´s,1 M. Placidi,1 J. Llobet,1 N. Baron,2,3 S. Chenot,2 Y. Cordier,2 J. C. Moreno,2 P. M. Gammon,4 M. R. Jennings,4 M. Porti,5 A. Bayerl,5 M. Lanza,5 and M. Nafrı´a5

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Micro and nano analysis of 0.2 mm Ti/Al/Ni/Au ohmic contact to AlGaN/GaN

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  1. Micro and nano analysis of 0.2 mm Ti/Al/Ni/Au ohmic contact to AlGaN/GaN A. Fontsere`,1,a) A. Pe´rez-Toma´s,1 M. Placidi,1 J. Llobet,1 N. Baron,2,3 S. Chenot,2 Y. Cordier,2 J. C. Moreno,2 P. M. Gammon,4 M. R. Jennings,4 M. Porti,5 A. Bayerl,5 M. Lanza,5 and M. Nafrı´a5 APPLIED PHYSICS LETTERS 99, 213504 (2011) 報告者: W.C.Jian

  2. Outline • Introduction • Experiment • Conclusion

  3. Introduction • As GaN technology continues to gain popularity, it is necessary to control the ohmic contact properties and to improve device consistency across the whole wafer. • In this paper, we use a range of submicron characterization tools to understand the conduction mechanisms through the AlGaN/GaN ohmic contact. • Our results suggest that there is a direct path for electron flow between the two dimensional electron gas and the contact pad. The estimated area of these highly conductive pillars is around 5% of the total contact area.

  4. Experiment • I-V curve, TLM, 接觸電阻結果 • Typical I-V-T • measurement • and • (b) and (c) shows • the RT, Rsh, and • Rc evolution with • temperature.

  5. Experiment • SEM & FIB 量測結果 TLM SEM cross section images of the Ti/Al/Ni/Au ohmic contact annealed at 750 C for 30 s. (a) View of the FIB machined lamella still anchored, (b) detailed view of the different layers, and (c) an enlarged image of the ohmic contact area.

  6. Experiment • EDX data EDX analyses at five distinct ohmic contact regions named C1, C2, C3, C4, and C5 (depicted in Fig. 2(c)). EDX relative composition for Ti, Al, Ni, and Au is included in the table on the right.

  7. Experiment • TEM data Cross sectional TEM images of the (a) Ti/Al/Ti/Au contact annealed at 750 C for 30 s and (b) detailed image of region C5.

  8. Experiment • AFM & SEM data (a) Topography and (b) current map of TLM surface taken with the cAFM for the 1.0 0.5 lm2 scan. (c) SEM image of FIB partial etch on TLM surface.

  9. Experiment • AFM & SEM data (a) Topography and (b) current map of lamella crosssection taken with the cAFM for the 0.55 0.55 lm2 scan.

  10. Conclusion • The submicron features of a typical Ti/Al/Ni/Au ohmic contact to AlGaN/GaN, with reduced Rc of 0.2X mm, have been investigated in detail. • This included TLM vs T, in the temperature range of 25 C–300 C and a range of physical analysis tools like SEM, FIB, TEM, and cAFM. • The results suggest that the preferential contact Mechanism is a direct electron path between the electrons of the 2DEG and the metal stack, though only a small part of the contact is actually conducting.

  11. Thanks for your attention

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