Should we create a Doorway page?

Hi Friends,

I am working on a website that has now diversified into two different niches, but both are doing good. Actually, the issue is that I have a website that belongs to niche A and I have a niche B page as well which is doing great. So I was thinking to create a subdomain and redirect it to niche B page, will that count as a Doorway Page, and in that case will there be any penalty by Google?

Any help will be appreciated ... Thanks

Or you can test it out and see what happens