在本論文中，我們研究以「分子束磊晶法」成長的對稱式結構的摻雜通道層和有摻雜氮的InGaAsN通道的結構，來改善電晶體其閘極工作電壓擺幅。
　　第一部分我們使用變化銦成分的對稱式摻雜結構的通道層，傳導帶將會形成V字型的谷，而通道中的電子會聚集在V型的谷底，因此二維電子雲會較遠離AlGaAs /InGaAs的接面，庫侖散射（Coulomb scattering）會降低，而提高其閘極工作電壓擺幅（gate voltage swing）。在室溫下，閘極的尺寸為1.2×100 μm2時，元件的閘極工作電壓擺幅逹1.75伏特，同時對稱式的摻雜通道結構的通道層會增加電子遷移率，所以可獲得較高的電流密度和增益。
　　第二部分,傳統以AlGaAs/InGaAs的HEMT缺點即為閘極工作電壓擺幅太小。我們在砷化銦鎵中加入適量的氮，以得到和砷化鎵晶格匹配且能隙可大幅縮減的四元化合物半導體材料-砷氮化銦鎵。所造成的大導帶差異使得砷氮化銦鎵在改善閘極工作電壓具明顯改善。在室溫下，閘極的尺寸為1.2×100 μm2時，元件的閘極工作電壓擺幅可逹1.15伏特，比傳統的AlGaAs/InGaAs的HEMT 優異。
　　此外使用變化銦成分的對稱式摻雜通道層結構在交流特性上都可以比傳統摻雜式通道表現的更佳。其截止頻率與最大振盪頻率分別可達11.2 GHz與26.7 GHz。元件輸出功率為12.54 dBm 而相關的附加功率效率為48%，線性功率增益為17.49 dB,在2.4 GHz時得其最小的雜訊為2.52 dB

　　In this thesis, we utilized symmetric doped channel structure and InGaAsN channel layer that contains dilute nitride material, both grown by Molecular beam epitaxy (MBE), to improve gate voltage swing.
　　In the first part , we use the symmetric doped channel by changing the In composition. The electrons in the channel will be confined well in the bottom of the V-shape conduction band. Thus, in the meantime the electrons are less closer to the AlGaAs/InGaAs interface, and Coulomb scattering lower down. Consequently, the gate voltage swing will increase. When the gate dimension is 1.2×100 μm2 at room temperature, the gate voltage swing will reach to 1.75 V . At the same time , the electron mobility will increase in the channel layer of symmetric doped channel structure, the higher drain current density and electron mobility can be obtained.
　　In the second part, the shortcoming of conventional AlGaAs/InGaAs HEMT is that the gate voltage swing is too small. By incorporating InGaAs with a proper amount of N, a quaternary material lattice-matched to GaAs can be obtained with a significant energy bandgap reduction. An increase of the conduction band offset makes the InGaAsN alloy obvious for improving gate voltage swing. When the gate dimension is 1.2×100 μm2 at room temperature, the gate voltage swing will reach to 1.15 V.
　　We also can find the result of AC characteristics of graded-composition symmetric doped channel FET is better than that of conventional doped channel FET. The current gain cut-off frequency (ft) and maximum oscillation frequency (fmax) are 11.2 GHz and 26.7 GHz, respectively. The device exhibited an output power of 12.54 dBm. The associated power-added efficiency is 48%, and the linear power gain is 17.49 dB. At 2.4 GHz, the minimum noise figure is 2.52 dB.

[1] R. Dingle, H. L. Stormer, A. C. Gossard, and W. Wiegmann, “Electron mobilities in modulation-doped semiconductor heterojuncyion superlattices,” Appl. Phys. Lett. , vol. 33, p. 665, 1978.

[2] W. C. Hsu, C. L. Wu, M. S. Tsai, C. Y. Chang, W. C. Liu, and H. M. Shieh, “Characterization of high performance inverted delta-modelation-doped (IDMD) GaAs/InGaAs pseudomorphic heterostructure FET’s,” IEEE Trans. Electron Devices vol. 42, p. 804, 1995.

[3] D. H. Park, and K. F. Brennan, “Theory of electronic transport in two-dimensional Ga0.85In0.15As/Al0.15Ga0.85As pseudomorphic structure,” J. Appl. Phys., vol. 65 (4), p. 1615, 1989.

[4] F. Ali and A. Gupta, “HEMTs and HBTs; devices, fabrication, and circuits,” Artech House, Boston London, 1991.

[5] H. Hida, , A. Okamoto, H. Toyoshima, K. Ohata, “A high-current drivability i-AlGaAs/n-GaAs doped-channel MIS-like FET(DMT) ,” IEEE Electron Device Lett., EDL-7(11), p. 625, 1986.

[6] H. Hida, , A. Okamoto, H. Toyosima, and K. Ohata, “An investigation of i-AlGaAs/n-GaAs doped-channel MIS-like FETs(DMT’s)-properties and performance potentialiyies,” IEEE Trans., ED-34,(7), p. 1448, 1987.

[7] B. Kim, R. J. Matyi, M. Wurtele, K. Bradshaw, M. A. Khatibazadeh, and H. Q. Tserng, “Millimeter-wave power operation of an AlGaAs/InGaAs/GaAs quantum well MISFET,” IEEE Trans. Electron Devices, vol. 36, p. 2236, 1989.

[8] P. P. Ruden, M. Shur, A. I. Akinwande, D E. Grider, and J. Beak, “AlGaAs/InGaAs/GaAs quantum well doped channel heterostructure field effect transistors,” IEEE Trans. Electron Devices, vol. 37, p. 2171, 1990.

[9] M. T. Yang and Y. J. Chan, “AlGaAs/InxGa1-xAs (0<x<0.25) doped-channel FET’s,” submitted for publication.

[10] Y. J. Chan, M. T. Yang T. J. Yeh, and J. I. Chyi, “High uniformity of AlGaAs/In0.15Ga0.85As doped-channel structures grown by MBE on 3 GaAs substrates,” J. Electronic MATERIALS, vol. 23, p. 675, 1994.

[11] L. W. Laih, S. Y. Cheng, W. C. Wang, P. H. Lin, J. Y. Chen, W. C. Liu, and W. Lin, “High-performance InGaP/InGaAs/GaAs step-compositioned doped channel field-effect transistor (SCDCFET),” Electron. Lett., vol. 33, (1) p. 98, 1997.

[12] J. C. Liou, and K. M. Lau, “Temperature dependence and persistent conductivity of GaAs MESFET’s with superlattice Buffers,” IEEE Trans. Electron Devices vol. 35, p. 14, 1988.

[13] W. C. Hsu, H. M. Shieh, M. J. Kao, R. T. Hsu, Y. H. Wu, “On the improvement of gate voltage swings in δ-doped GaAs/In xGa1-xAs/GaAs pseudomorphic heterostructures,” IEEE Trans. Electron Devices vol. 40, p. 1630, 1993.

[14] C. L. Wu, W. C. Hsu, H. M. Shieh, M. S. Tsai, “An improved inverted δ-doped GaAs/InGaAs pseudomorphic heterostructure grown by MOCVD,” IEEE Electron Device Lett., vol. 15, p. 330, 1994.

[15] M. Feng, D. R. Scherrer, P. J. Apostolakis, J. W. Kruse, “Temperature dependent study of the microwave performance of 0.25 μm gate GaAs MESFETs and GaAs pseudomorphic HEMTs,” IEEE Trans. Electron Devices vol. 43, p. 852, 1996.

[16] 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.

[17] K. Kiziloglu, H. Ming, D. S. Harvey, R. D. Widman, C. E. Hooper, P. B. Janke, J. J. Brown, L. D. Nguyen, D. P. Docter, S. R. Burkhart, “High-performance AlGaAs/InGaAs/GaAs PHEMTs for K and Ka-band applications,” Microwave Symposium Digest, IEEE MTT-S International, Vol. 2 , p. 13, 1999.

[18] M. Miyashita, N. Yoshida, Y. Kojima, T. Kitano, N. Higashisaka, J. Nakagawa, T. Takagi, M. Otsubo, “An AlGaAs/InGaAs pseudomorphic HEMT modulator driver IC with low power dissipation for 10-Gb/s optical transmission systems,” Microwave Theory and Techniques, IEEE Transactions on , Vol. 45 , p. 1058 ,1997.

[19] P. Cova, R. Menozzi, D. Lacey, Y. Baeyens, F. Fantini, “High performance electron devices for microwave and optoelectronic applications,” EDMO., IEEE 1995 Workshop on , 1995.

[20] W. H. Lan, W. J. Lin, C. K Peng, S. S. Chen, S. L. Tu, “Recessed-gate AlGaAs-InGaAs-GaAs pseudomorphic HEMT with Si-planar-doped etch stop layer,” Electronics Letters , Vol. 31 , p. 592 ,1995.

[21] J. H. Lee, H. S. Yoon, C. S. Park, H. M. Park. “Very low noise characteristics of AlGaAs/InGaAs HEMTs with wide head T-gate,” Device Research Conference, 1995. Digest. 1995 53rd Annual, p. 36, 1995.