在本論文中，我們研究以「分子束磊晶法」成長以InAlGaAs為緩衝層的In0.45Al0.55As/ In0.53Ga0.47As異變結構(metamorphic)高載子遷移率電晶體的特性。以InAlGaAs 當緩衝層不僅可以調和砷化鎵基板和主動層間的晶格不匹配，而且它的能隙比傳統的InAlAs 大，所以可以提供較好的緩衝層隔離減少漏電流。
　　我們分別在蕭基層鍍上金、鎳/金、鈦/金和鉑/金去研究元件的特性。由實驗結果顯示，當鍍在蕭基層上的金屬功函數不同時蕭基能障的高度也會隨著改變，當蕭基障變大時會使通道的空乏區増大，因而增進元件的夾止特性並提高崩潰電壓的值。通道的空乏區増大也會抑制通道中載子的量使衝擊游離化的效應減低，進而使紐結效應(kink effect)跟著減小。
　　在文中，我們討論在室溫下，閘極的尺寸為1.2×100 μm2，在蕭基層鍍上不同金屬時元件的最大汲極飽和電流、異質轉導值和崩潰電壓，我們也同時描述了元件的高頻，功率和雜訊的特性。
　　使用鉑/金當蕭基接觸的異變結構高載子遷移率電晶體顯示了良好的特性，我們預期可以藉由蕭基層薄化做出增強型電晶體並使元件可以利用於高速和放大器的應用。

　　In this thesis, the characteristics of the In0.45Al0.55As/ In0.53Ga0.47As metamorphic high electron mobility transistors (MHEMT’s) with InAlGaAs buffer layer grown by Molecular beam epitaxy (MBE) have been studied. The InAlGaAs buffer layer in this structure not only accommodates the large lattice mismatch between the active layers and the GaAs substrate, but also replaces the InAlAs buffer layer as in the conventional design. The band gap of the InAlGaAs buffer layer is comparable or greater than the InAlAs band gap which resulted in good buffer layer isolation.
　　We evaporated Au，Ni/Au，Ti/Au and Pt/Au as the Schottky contacts. The results show that different metal work function can get different Schottky barrier heights， the Schottky barrier heights increase can make the channel’s depletion region increase and enhance the pinch-off characteristics and the breakdown voltages obviously. The channel’s depletion region increases also can suppress impact ionization and kink effect，because the carriers in channel decrease.
　　For a 1.2×100 μm2 gate dimension, the maximum saturation drain current density，extrinsic transconductance and breakdown voltage with different Schottky contacts have been described. The microwave，power and noise performances of the In0.45Al0.55As/ In0.53Ga0.47As metamorphic high electron mobility transistors have also been discussed.
　　These good performances show that the studied structure with Pt/Au as the Schottky contact has good potential for high speed and amplification capability，and to realize the enhancement-mode device by making the Schottky contact thinner can be expected.

[1] S. M. Sze, Physics of Semiconductor Devices, 2nd ed., Wiley, New York, 1981.
[2] G. C. Dacey and I. M. Ross, “Unipolar field-effect transistor,” Proc. IRE 41, 970 (1953).
[3] T. Mimura, S. Hiyamizu, T. Fujii, and K. Nanbu, “a new Field-Effect Transistor with Selectively Doped GaAs/n-AlxGa1-xAs Heterojunctions”, Jap. J. Appl. Phys. vol.19, no. 5, p.L225-L227, 1980.
[4] S. Karmalkar, G. Ramesh, “A simple yet comprehensive unified physical model of the 2D electron gas in delta-doped and uniformly doped high electron mobility transistors,” IEEE Trans. Electron Devices, vol. 47, p.308, 2000.
[5] Y. Ando, T. Itoh, “Accurate modeling for parasitic source resistance in two-dimensional electron gas field-effect transistors,” IEEE Trans. Electron Devices, vol. 36, p.1036, 1989.
[6] L. D. Nguyen, W. J. Schaff, P. J. Tasker, A. N. Lepore, L. F. Palmateer, M. C. Foisy, L. F. Eastman, “Charge control, DC, and RF performance of a 0.35 um pseudomorphic AlGaAs/InGaAs modulation-doped field-effect transistor,” IEEE Trans. Electron Devices, vol. 35, p.139, 1988.
[7] Behet, M., Van Der Zanden, K., Borghs, G., and Behres, A., “Metamorphic InGaAs/InAlAs quantum well structure grown on GaAs substrate for high electron mobility transistor applications,” Appl. Phys. Lett., 1998, 73, p. 2760-2762.
[8] Contrata, W., Iwata, N., “Double-doped In0.35Al0.65As/In0.35Ga0.65 As power heterojunction FET on GaAs substrate with 1 W output power,” Electron Device Letters, IEEE ,vol. 20 , July 1999 p.369 – 371.
[9] Hoke, W.E., Lemonias, P.J., Lyman, P.S., Torabi, A., Marsh, P.F., Mctaggart, R.A., Lardizabal, S.M., and Hetzler, K., “Molecular beam epitaxial growth and device performance of metamorphic high electron mobility transistor structures fabricated on GaAs substrates,” J. Vac. Sci. Technol. B, 1999, 17, p.1131-1135.
[10] Fazal Ali and Alitya Gupta, “HEMTs and HBTs; Devices, Fabrication, and Circuits”, p.82
[11] M.Hueschen, N. Moll, E. Gowen, and J.Miller, “Pluse Doped MODFET’s”, IEEE, IDEM Technical Digest, p.438, 1984.
[12] A. Fathimulls, J.Abrahams, T. Loughran, H. Hier, “High performance InAlAs/InGaAs HEMTs and MESFETs”, IEEE Electron Device Letters, vol.28,no. 19, p.1849,1992.
[13] S.R. Bahl, J. A. del Alamo, “Elimination of mesa sidewall gate leakage in InAlAs/InGaAs HFETs”, IEEE Trans. On Electron Devices, vol. 13, no. 4, p.195, 1992.
[14] S. R. Bahl, M. H. Leary, J. A. del Alamo, “Mesa sidewall gate leakage in InAlAs/InGaAs HFETs”, IEEE Trans. on Electron Devices, vol. 39, no. 9, p.2037, 1992.
[15] W. C. Hsu, C. L. Wu, M. S. Tsai, C. Y. Chang, W. C. Liu, H. M. Shieh, “Charactezation of high performance inverted delta modulation doped (IDMD) GaAs/InGaAs psedomophic heterostructure FETs”, IEEE Trans. on Electron Devices, vol 9, no. 1, p22, 1993.
[16] G. I. Ng, W. P. Hong, D. Pavlidis, M. Tutt, P. K. Bhattacharya, “Characteristics of stained InGaAs/InAlAs HEMT with optimized transport parameters”, IEEE Electron Device Letters, vol. 9, no. 9, p439, 1988.
[17] S. R. Bahl, B. R. Bennett, J. A. Alamo, “Doubly stained InAlAs/n-InGaAs HFET with high breakdown voltage”, IEEE Electron Device Letters, vol. 14, no. 1, p. 22, 1993.
[18] Suemitsu, T., Enoki, T., Sano, N., Tomizawa, M., Ishii, Y., “An analysis of the kink phenomena in InAlAs/InGaAs HEMT's using two-dimensional device simulation,” Electron Devices, IEEE Transactions on ,vol. 45 , no. 12 , Dec. 1998 p.2390 – 2399.
[19] Somerville, M.H., Ernst, A., del Alamo, J.A., “A physical model for the kink effect in InAlAs/InGaAs HEMTs,” Electron Devices, IEEE Transactions on ,vol. 47 , no. 5 , May 2000 p.922 – 930.
[20] Horio, K., Wakabayashi, A., “Numerical analysis of surface-state effects on kink phenomena of GaAs MESFETs,” Electron Devices, IEEE Transactions on ,vol. 47 , no. 12 , Dec. 2000 p.2270 – 2276.
[21] Haruyama, J., Negishi, H., Nishimura, Y., Nashimoto, Y., “Substrate-related kink effects with a strong light-sensitivity in AlGaAs/InGaAs PHEMT,” Electron Devices, IEEE Transactions on ,vol. 44 , no. 1 , Jan. 1997 p.25 – 33.
[22] W. C. Liu, W. L. Chang, W. S. Lour, S. Y. Cheng, Y. H. Shie, J. Y. Chen, W. C. Wang, H. J. Pan, “Temperature-Dependent Investigation of a High-Breakdown Voltage and Low-Leakage Current In0.49Ga0.51P/In0.15Ga0.85As Pseudomorphic HEMT”, IEEE Electron Device Letters, vol. 20, p. 274, 1998.
[23] R. Menozzi, M. Borgarino, Y. Baeyens, M. Van Hove, F. Fantini, “On the effects of hot electrons on the DC and RF characteristics of lattice-matched InAlAs/InGaAs/InP HEMTs”, IEEE Microwave and Guided Wave Lett., vol. 7, p. 3, 1997.
[24] M. Feng, D. R. Scherrer, P. J. Apostolakis, J. W. Kruse, “Temperature dependent study of the microwave performance of 0.25um gate GaAs MESFETs and GaAs pseudomorphic HEMTs”, IEEE Trans. Electron Devices, vol 43, p.852, 1996.
[25] N. Harada, S. Kuroda, T. Katakami, K. Hikosaka, T. Mimura, and M. Abe, “Pt-based gate enhancement-mode InAlAs/InGaAs HEMT’s for large-scale integration,” in Proc. 3rd Int. Conf. InP and Related Materials, 1991, p. 377-380.
[26] A. Belache, A. Vanoverschelde, G. Salmer, M. Wolny, “Experimental analysis of HEMT behavior under low-temperature conditions”, IEEE Trans. Electron Devices, vol. 38, p. 3, 1991.