how to settle boundary conditions in a RTP process

Young

Hi,everyone:

I am currently building a simulation for a rapid thermal process. The system consists of two banks of lamps, one on each side of a silicon substrate. The chamber is filled with air. I consider the main heat transfer mode is radiation. So DO radiation model is used in my setting. I set the lamp temperature at 2500K in the "Temperature" settings under "wall" boundary condition. To receive the radition from the lamp, how to set the boundary conditions of the substrate(both the wall and the solid volume)?

I set the solid volume to "participate in radiation". The substrate surface type as "wall" and choose "Radiation" under "Thermal" tab by define the external radiation temperature as same as lamps. However, I get strange results.

Please tell me if you know how the settle the boundary conditions or the wrong part in my settings. Thanks.