To do a phD in Biotechnology you have to ways to go:

1. If you pursue BTech in Biotechnology then you will be eligible for Integrated PhD program in Biotechnology after the completion of your BTech course. If not then you can try for MTech and after successfully qualifying MTech you can surely join for PhD.

2. The second way is if you pursue BSc Biotechnology then usually you have to pursue MSc and then you can go for PhD. Although there can be some colleges which may offer your Integrated course after BSc but this are mainly private universities.

I hope my answer helps you. All the very best for your future endeavors!