In high power devices application, the Si-MOSFET is the most used until now. Recently, GaN-MEMT shows a spectaculaire properties which allows it to replace the Si-MOSFET in the few next years. Then, my question is : why MOSFET is used for Si while HEMT is used for GaN?
It may not be much help but there is a major 'fashion for MOSFETS' which you hear about in relevent conferences. I'm no specialist but I expect that means the technology is well developed (including on an Industrial scale). On the other hand, I have not heard much about HEMT. Maybe you could ask 'How well is the GaN production known in Industry and can GAN MOSFETs be made (easily)? How aboit other methods?
Its not complicated. The MOSFET uses the unique properties of the Si/SiO2 interface [low surface state density] to effectively control charge density and current flow in the source-drain channel. No equivalent situation exists in the compound semiconductor [CS] family due to the lack of suitable native oxides. However, CS can use bandgap engineering to produce heterostructures which are not readily achieved in Si technology [if you exclude Si/Ge]. So MOSFET for Si and HEMT for CS.
Yes, Peter is correct. To add to the answer, the 2D electron gas for the HEMT can be modulated much more quickly. The wide band gap of GaN also allows higher temperature and higher voltage operation than silicon. The higher frequency and higher voltages also enable simpler circuit topologies. Generally speaking for power electronics GaN should replace Silicon for voltages in the 600-1200 V rage. Above 1200 V silicon carbide MOSFETs will be better.
It is an interesting question because the the technologies are still being developed and there is lot of competition between silicon, GaN and Silicon Carbide.
Lets say, GaN HEMT uses 2D Electron gas state (2DEG) which is a product of specific lattice structure of GaN.
To improve carriers mobility at nano-scale MOSFETs we use Strained silicon technology.
Physics for 2DEG and Strained silicon are similar - reduction for carrier scattering at one dimension improves mobility.
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