Oki's GaN HEMT delivers record transconductance
Oki Electric has developed a GaN HEMT on a silicon substrate that is claimed to offer dramatically improved amplifying characteristics.
The transistor delivers a fmax of 115 GHz and a record transconductance of 350mS/mm.
And because the device is fabricated on a silicon substrate instead of SiC manufacturing costs are said to be reduced by 50%.
"By enhancing the output of transistors based on this technology, we can contribute to the acceleration of WiMAX and next generation wireless communication systems," said Harushige Sugimoto, Oki Electric's chief technology officer.
The company plans to start volume shipments of these products in 2007.
As well as the record transconductance, the latest devices have significantly higher fmax values, which are comparable to HEMTs produced on SiC. Previous GaN HEMTs on silicon had fmax values of only 70-80 GHz.
Oki says that the increased performance results from improved crystal growth technology for GaN on silicon, which led to a higher electron mobility, and better device design.
The latest HEMTs contain gate electrodes formed on recessed structures that enable the gate length to be reduced to 0.2 µm, as well as ohmic electrodes formed on a recessed structure.
