Matsushita team claims power switch advance
Matsushita Electric researchers claim to have developed the world s first "vertical" GaN transistor that can be used in high-power switching devices.
According to the company, the new design dramatically reduces the surface area of the devices compared with the regular planar arrangement, potentially allowing many more transistors to be produced on a single wafer.
The transistor is also said to feature a 0.3 µm-wide channel that yields the good pinch-off characteristics that are important for power switching applications.
To produce the vertical transistor, the Matsushita team developed a new epitaxial growth strategy. The quaternary InAlGaN alloy that they use in the contact layer is said to enable a contact resistance that is 33 percent lower than normal because it reduces the barrier height from the electrode.
Matsushita also claims that the phenomenon of current collapse, which has proved to be a problem for GaN-based transistors, can be suppressed with the new design. Because the vertical transistor has a much smaller surface area than normal, the effect of surface traps is much less pronounced.
Current collapse can result from other effects in the bulk structure, however.
GaN-based transistors for RF applications have recently been launched commercially by RF Micro Devices and Cree, while Japanese companies including Toshiba and Eudyna Devices are actively pursuing the technology too.
However, SiC-based devices are more typically used for high-performance power electronics at the moment. The Emcore spin-off company Velox Semiconductor (see related story) is one of the few that is focused on the production of GaN-based high-power switches.
