InAlAs/InGaAs metamorphic high electron mobility transistor with InAlGaAs buffer layer

• Main Authors: Ching-Hsiang Tseng, 曾靖翔
• Other Authors: Wei-Chou Hsu
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/z38v8q

碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 92 === 　　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.