Boron can be made conducting as well so same problem as carbon. It can gum up the insulator and ruin the breakdown along the insulator. Any gas that can decompose into a solid has the potential to gum up the process. This is a common problem in the semiconductor industry with silane and large molecules that contain silicon. I think you will get some shots before it becomes a problem but operating at steady state could be challenging. High temperature will only improve the bonding of boron atoms and grow dense thin films.
