| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 91 === In this thesis, the high electron mobility transistors (HEMT’s) with step-composition channel grown by metalorganic chemical vapor deposition (MOCVD) have been studied. The improvement can be expected by using a novel channel structure.
By using the step graded channel the electrons in the channel will be confined well in the bottom of the V-shape conduction band. The electrons are also far away from the AlGaAs/InGaAs interface, thus Coulomb scattering is reduced. Consequently the electron mobility will increase. Then the high drain current density and large gate voltage swing can be obtained.
For a 1.2×100 μm2 gate dimension, the maximum saturation drain current density is 385 mA/mm and the maximum extrinsic transconductance is 148 mS/mm along with the gate voltage swing of 1.9V. Besides, the gate-to-drain breakdown voltage of 16 V is obtained.
The microwave performance of our structure is also described. The current gain cut-off frequency ( ) and maximum oscillation frequency ( ) are 9.5 GHz and 37 GHz, respectively.
These good performances show that the studied structure with step-composition channel HEMT has good potential for high speed and amplification capability.
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