HEMT Grid Example

This first section defines the vertical grid structure.

   line x loc=-0.3 spac=0.01 tag=MetTop
   line x loc=-0.1 spac=0.01 
   line x loc=0.0 spac=0.001 tag=AlGaNTop
   line x loc=0.015 spac=0.0008 tag=AlGaNBottom
   line x loc=1.8 spac=0.2 tag=GaNBottom
   line x loc=2.0 spac=0.02 tag=AlNBottom
   line x loc=3.0 spac=1.5 tag=BBottom

We are defining a multiple material stack. The 0.0 is the top of the semiconductor stack. The MetTop line will be where the top of the gate is and the top of the nitride on either side of the gate. We then define a layer of 15nm of AlGaN buffer layer. Below this is GaN and below that is a SiC layer that will be defined. The current is carried near the AlGaN / GaN interface, so the smallest grid spacing is there.

   line y loc=-2.0 spac=0.05 tag=Left 
   line y loc=-1.25 spac=0.5 
   line y loc=-0.5 spac=0.001 tag=Oxleft
   line y loc=-0.2 spac=0.1
   line y loc=0.0  spac=0.001
   line y loc=0.2 spac=0.1
   line y loc=0.5 spac=0.001 tag=Oxright
   line y loc=1.25 spac=0.5
   line y loc=2.0 spac=0.05 tag=Right  

The center of the device is 0.0 and has a fine spacing. The source and drain are going to be symmetrically placed at -2.0um and 2.0um. The gate will be 1.0um wide. We have a finer grid in the middle of the device gate and at the source and drain edge of the gate.

   region SiC xlo=GaNBottom xhi=BBottom ylo=Left yhi=Right
   region GaN xlo=AlGaNBottom xhi=GaNBottom ylo=Left yhi=Right
   region AlGaN xlo=AlGaNTop xhi=AlGaNBottom ylo=Left yhi=Right
   region Metal xlo=MetTop xhi=AlGaNTop ylo=Oxleft yhi=Oxright
   region Nitride xlo=MetTop xhi=AlGaNTop ylo=Left yhi=Oxleft
   region Nitride xlo=MetTop xhi=AlGaNTop ylo=Oxright yhi=Right

The regions are defined using the tags defined above.

   init quad               

The resulting grid will look like this: File:HEMT grid.jpg