| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所 === 103 === Conventional AlGaN/GaN high electron mobility transistors (HEMTs) are depletion-mode (D-mode) HEMTs due to the inherent two-dimensional electron gas (2DEG) induced by polarization effects. It is necessary to apply a negative gate bias to turn off a D-mode HEMT, and that will cause additional power loss. Therefore, the enhancement-mode (E-mode) HEMT is developed to reduce extra power consumption. Moreover, the E-mode HEMT is also required for circuit simplicity and fail-safe operation.
In the thesis, gate recess process was used to convert a depletion-mode HEMT to an enhancement-mode HEMT through the reduction of the 2DEG density under the gate region. To suppress gate leakage current, a ZrO2 film was deposited as a gate dielectric by using liquid-phase deposition (LPD) method. Besides, in order to investigate the electrical characteristics of HEMTs, we presented an analytical model based on the gradual channel approximation to simulate the drain current and transconductance. In addition, the simulation results were compared with experimental data.
The E-mode AlGaN/GaN MOSHEMT was achieved by using gate recess technique and the LPD process. The threshold voltage is successfully shifted to 0.3 V. The maximum drain current density reaches about 347 mA/mm. The maximum transconductance is 146 mS/mm. The Ion/Ioff ratio and the subthreshold swing are improved to 1.4×108 and 89 mV/dec. The gate leakage current and the breakdown voltage are 2.06×10-7 A/mm and 92 V,respectively.
|
|---|
