氮化鎵材料的寬能隙、高臨界電場、高電子飽和速度和高導熱係數 材料特性使其在高速及高頻元件領域內成為相當熱門的研究主題。其中， 由氮化鋁銦作為阻障層的氮化鋁銦/氮化鎵異質接面場效電晶體由於晶格 匹配，無應力問題，且其自發性極化產生相當高的二維電子氣濃度，使 其在非常適合用於高頻元件。然而其漏電流特性使之不易達到如氮化鋁 鎵/氮化鎵元件可以達到的高壓特性。

本篇論文透過改變閘極蝕刻深度和沉積氧化鋁絕緣層，形成金屬— 絕緣層—半導體高電子遷移率電晶體，藉此提高其崩潰電壓。並維持其 高頻特性。透過元件製程並量測，雖然由於氧化鋁絕緣層沉積後，在金 屬—絕緣體接面和絕緣體—半導體接面之間產生的缺陷，以及閘極蝕刻 深度未最佳化，導致元件的直流特性不佳，但實驗結果仍證明沉積氧化 鋁絕緣層能有效的提高元件的崩潰電壓，其中最好的元件表現提升了
62.5%，而高頻的部分則可達到 f max = 4.38GHz 和 f T = 1.95GHz。若進
一步最佳化蝕刻深度並在氧化鋁絕緣層沉積後進行退火減少缺陷，可預 期元件表現能更為提升。

Research in high power and high frequency devices on Gallium-Nitride- based High Electron Mobility Transistor(HEMT) has become more and more popular due to their outstanding material characteristics which including wide bandgap, high critical electric field, high electron saturation velocity, and high thermal conductivity. Among them, owing to the high density of two-dimension electron gas only depending on the spontaneous polarization without strain introduced by lattice match, the InAlN/GaN Heterojunction Field Effect Transistor using InAlN as barrier layer is suitable for high frequency applications. However, the high leakage current and low breakdown of InAlN/GaN device is still an issue for achieving high power performance.

In this thesis, MIS-HEMT using Al2O3 as the insulator layer with different
gate recess depths was investigated to increase the breakdown voltage while
maintaining good high frequency performance. The defects and traps generated at
the Metal-Insulator interface and Insulator-Semiconductor interface and the non-
optimized gate recess depth could be responsible to the relatively poor DC
performance of the transistors. However, the result still shows that using Al2O3 as
insulator layer can improve the breakdown voltage up to 62.5%. In addition,
device achieves frequency performance with f_max=4.38GHz and
f_T = 1.95GHz. With optimizing the depth of gate recess and annealing device after the deposition of Al2O3 insulator layer, the improvement of performance can be expected.

[1] K. Shinohara, et al., "Deeply-scaled E/D-Mode GaN-HEMTs for sub-mm- wave amplifiers and mixed-signal applications." Compound Semiconductor Integrated Circuit Symposium (CSICS),2012, IEEE. IEEE, 2012.
[2] J.A. del Alamo, et al., “GaN HEMT reliability,” Microelectronics Reliability, vol. 49, Issues 9-11, Nov. 2009.
[3] A. Crespo, et al., “High frequency performance of Ga free AlInN/GaN HEMT,” The 36th International Sysmposium on Compund Semiconductors 2009.
[4] B. Gelmont, et al., “Monte carlo simulation of electron transport in gallium nitride,” J. Appl. Phys., 74 (3), pp. 1818-1821, 1993
[5] B. J. Baliga, “Trends in power semiconductor devices,” IEEE Transaction on Electron Devices, 43(10), pp. 1717-1731, 1996.
[6] J. Kuzmik, “InAlN/(In)GaN high electron mobility transistors: some aspects of the quantum well heterostructure proposal,” Semicond. Sci. Technol. 17 (2002)540.
[7] J. Kuzmik, “Power electronics on InAlN/(In)GaN: Prospect for a record performance,” IEEE Electron Device Lett., vol. 22, no. 11, pp. 510– 512,Nov. 2001.
[8] O. Jardel, et al., “Electrical performances of AlInN/GaN HEMTs. A comparison with AlGaN/GaN HEMTs with similar technological process,” International Journal of Microwave and Wireless Technologies (2011), Vol.3, issue 3, pp 301-309.
[9] Y. Cao, et al., ”Ultrathin MBE-Grown AlN/GaN HEMTs with record high current densities.” in Proc. Int. Semicond. Device Res.Symp., College Park, MD, 2007, pp. 1–2.
[10] J. S. Xue, et al., “Effect of high temperature AlN interlayer on the performance of AlGaN/GaN properties,” IEEE International Conference of Electron Devices and Solid-State Circuits, 2009., vol., no., pp.416,418, 25-27 Dec. 2009.
[11] M. Gonschorek, et al., “High electron mobility lattice-matched AlInN/ GaN field-effect transistor heterostructures,” Applied Physics Letters , vol. 89, no.6, pp.062106,062106-3, Aug 2006.
[12] J. Q. Xie, et al., “High electron mobility in nearly lattice-matched AlInN/ GaN heterostructure field effect transistors,” Appl. Phys. Lett., vol. 91, no. 13, Sep. 2007,Article 132116.
[13] Y. Li, et al., “Alloy disorder scattering limited mobility of two-dimensional electron gas in the quaternary AlInGaN/GaN heterojunctions,” Physica E: Low- dimensional Systems and Nanostructures, Volume 67, March 2015.
[14] I. B. Rowena, et al., “Buffer thickness contribution to suppress vertical leakage current with high breakdown field (2.3 MV/cm) for GaN on Si,” IEEE Electron Device Lett., vol. 32, no. 11, pp. 1534–1536, Nov. 2011.
[15] S. L. Selvaraj et al., “1.4-kV Breakdown voltage for AlGaN/GaNhigh- electron- mobility transistors on silicon substate,” IEEE Electron DeviceLett., vol. 33, pp.1375 -1377, 2012.
[16] G. H. Jessen, et al., “Short-channel effect limitations on high- frequency operation of AlGaN/GaN HEMTs for T-gate devices,” IEEE Trans. Electron Devices, vol. 54, no. 10, pp. 2589–2597, Oct. 2007.
[17] J. Y. Shiu, et al., “Oxygen ion implantation isolation planar process for AlGaN/GaN HEMTs,” IEEE Electron Device Letter, vol. 28, no. 6, pp. 476-478, Jun. 2007.
[18] T. Oishi, et al., “Highly resistive GaN layers formed by ion implantation of Zn along the c-axis,” J. Appl. Phys., vol. 94, no. 3, pp. 1662-1666, Aug. 2003.
[19] B. Boudart, et al., “Raman characterization of Mg+ ion-implanted GaN,” J. Phys., Condens. Matter, vol. 16, no. 2, pp. s49-s55, Jan. 2004.
[20] S. R. Bahl, et al., “Mesa-sidewall gate leakage in InAlAs/InGaAs heterostructure field effect transistors,” IEEE Trans. Electron Devices, vol. 39, no. 9, pp. 2037- 2043, Sep. 1992.
[21] Y. Lin, et al., “Schottky barrier height and nitrogen-vacany-related defects in Ti alloy,” J. Appl. Phys., vol. 95, 2004.
[22] D. Buttari, et al., “Systematic characterization of Cl2 reactive ion etching for improved ohmics in AlGaN/GaN HEMTs,” IEEE Electron Device Letters, vol. 23, no. 2, pp. 623-623, Feb. 2002.
[23] H. Tokuda, et al., “Role of Al and Ti for ohmic contact formation in AlGaN/GaN heterostructures,” Appl. Phys. Lett., vol. 101, no. 26, pp. 262104, 2012.
[24] M. Wang, et al., “900 V/1.6 mΩ·cm2 normally off Al2O3/GaN MOSFET on silicon substrate,” IEEE Trans. Electron Devices, vol. 61, no. 6, pp. 2035–2040, Jun. 2014.
[25] Y. Lu, et al., “Normally off Al2O3–AlGaN/GaN MIS-HEMT with transparent gate electrode for gate degradation investigation,” IEEE Trans. Electron Devices, vol. 62, no. 3, pp. 821–827, Mar. 2015.
[26] G. Koley, et al., “Slow transients observed in AlGaN/GaN HFETs: Effects of SiNx passivation and UV illumination,” IEEE Trans. Electron Devices, vol. 50, no. 4, pp. 886-893, Apr. 2003.
[27] S. Ohi, et al., “Effect of passivation films on DC characteristics of AlGaN/ GaN HEMT.” Future of Electron Devices, Kansai (IMFEDK), 2014 IEEE International Meeting for. IEEE, 2014.
[28] J. Bernat, et al., “Effect of surface passivation on performance of AlGaN/ GaN/Si HEMTs.” Solid-State Electronics 47.11 (2003): 2097-2103.
[29] S.M. Sze, Physics of Semiconductor Devices, 2nd Edition, John Wiley & Sons, Inc., 1981
[30] J. Kang, et al., “The characteristics of leakage current mechanisms and SILC effects of Al2O3 gate dielectric” ,2002.
[31] M. Choi, et al., “Impact of native defects in high-k dielectric oxides on GaN/oxide metal-oxide-semiconductor devices” Phys. Status Solidi B 250, No. 4, 787-791,2013
[32] I. Krylov, et al., “Indium outdiffusion and leakage degradation in metal/ Al2O3/In0.53Ga0.47As capacitors” Appl. Phys. Lett. 103, 053502 (2013)