Are these E-mode GaN-on-Silicon power devices a World first?
13-06-2017 | By Paul Whytock
E-mode 200 and 650Volt power devices that achieve a Ron dispersion of under 20% have been successfully developed using 200mm GaN-on-Silicon wafers.
The technology was created by nanoelectronics and digital technology specialists Imec who say it is ready for prototyping, customised low-volume production and technology transfer.
GaN (Gallium Nitride) technology is well documented as creating fast switching power devices with higher breakdown voltage and lower on-resistance than conventional silicon.
Of particular importance in a GaN device structure is the buffer layer. What this does is handle the large difference in lattice parameters and thermal expansion coefficients between the AlGaN/GaN materials system and the silicon substrate.
Imec says it achieved a breakthrough development in the buffer design which facilitated the creation of buffers suitable for developing 650Volt GaN devices on 200mm wafers. This characteristic was combined with a particular silicon substrate thickness and doping that was able to increase the GaN substrate yield on 200mm to what Imec describes as competitive levels. The consequence of this is it lowers the production cost of creating GaN devices.
Cutting the cost of exploiting the technical advantages of GaN has been an issue that technologists have long wrestled with.
GaN substrates using epitaxial methods have always been too pricey, as has the use of Silicon Carbide (SiC). What is important about this particular technology breakthrough is that whereas silicon has always been attractive price-wise marrying it up to GaN remained a tricky proposition because of the potential for defects to occur because of thermal and lattice inadequacies.
In addition to cutting the cost elements this Imec development has also optimised field plate design. This has contributed to the Ron dispersion rate of 20% up to 650Volt over a temperature range of 25° to 150°C. This means there is almost no change in the transistor on-state after switching from the off-state.
Imec’s says this GaN-on-Si device technology is a World first. It is also Au-free and compatible with the wafer processing systems in a silicon fab.
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