Characteristics of III- Nitride Metal Oxide Semiconductor Transistors on Different Substrates
Date Issued
2015
Date
2015
Author(s)
Lin, Bo-Ren
Abstract
This work is focused on the use of the photoelectrochemical oxidation (PEC oxidation) method on both AlGaN/GaN on sapphire substrate and gate recessed AlGaN/GaN on silicon substrate to realize metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs). First, the characteristics of PEC oxide layer and plasma enhanced atomic layer deposition oxide layer are compared. The measured results show that, with PEC oxidation, the current on/off ratio is increased from 7 to 8 order of magnitude and the gate leakage current is decreased almost 2 order of magnitude. Then, the effect of different PEC oxide thicknesses to MOS-HEMT performance are considered. We found that with the increasing of the thickness of PEC oxide, the threshold voltage is decreased first then shifted to -2V, which is related to the interface state of the PEC oxide and the AlGaN layer or the strain of the AlGaN layer induced by the PEC oxide. The measured results of gate recessed AlGaN/GaN MOS-HEMTs with PEC oxide layer and PE-ALD passivation layer show that the gate recess method can effectively shift the threshold voltage from -4 V to 1.5 V. However, the transconductance is decreased about 40%.
Subjects
HEMT
Type
thesis
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