Hii!
Yes, you can do b.tech after completing BCA, but that would again be start of your graduation and simply waste your years. Because, after completing your graduation in BCA, you would again be beginning graduation via b.tech.
So, instead of that, I would suggest you to join m.tech or MCA after completing BCA. This will lead you to higher studies and save your time, also giving you wide variety of career aspects ahead.
Hope this helps.
Good luck!