GaN Power Device Team
(1) Material science of GaN growth
(2) Development of AlGaN/GaN HEMT power switching devices
(3) Feasibility study of AlGaN/GaN HEMTs in switching regulators
Dr. M. Shimizu, E-mail: mitsu.shimizu(at)aist.go.jp
Dr. X. Q. Shen, E-mail: xq-shen(at)aist.go.jp
Dr. T. Ide, E-mail: t-ide(at)aist.go.jp
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(1)GaN growth on Si substrate using MOCVD
| In actual applications in power electronics based on low-cost markets,
the reduction of the device cost is important. The substrates using GaN
single crystals or the SiC crystals have been developed, however they are
very expensive. Thus the development of GaN growth on Si substrate with
low-cost is important. Recently the growth technique of the GaN on Si substrate
using the AlN/GaN super-lattice structure is developed by Prof. T. Egawa
In our group, MOCVD growth is employed for developing device structures, and the material science of the GaN growth on Si substrate has been investigated.
|Stress of GaN layer on Si substrate can be controlled using AlN/AlGaN super-lattice structure
|AFM measurement of GaN layer on Si substrate
Some defects can be found, but surface is flat.
Steps of lattice can be found.
GaN on Si substrate using AlN/GaN super-lattice
(2 mm X 2 mm, RMS = ~ 0.3 nm)
(2)Normally off operation
(1) p-InGaN cap layer under the gate electrode.
(2) HEMT using channel of AlGaN/GaN/AlGaN double hetero-structure.
| (A)p-InGaN cap layer under the gate electrode
|Drain voltage - drain current characteristics|
|(1)Threshold voltage : ~ 0.5 V
(2)Maximum drain current : > 200 mA / mm
(3)Maximum Gm : 120 mS/mm
(4)On-resistance Vg =3 V : 20 W/mm
|(B) HEMT with AlGaN/GaN/AlGaN double heterostructure|
|Drain voltage vs. current characteristics of DH HEMT|
(3)Development of Equivalent Circuit for AlGaN/GaN HEMT
Feasibility of AlGaN/GaN power device in switching regulators.
| (1) current collapse is included.
(2) leakage current in GaN layer under hetero-junction channel.
(3) 2-DEG model is included.