Yes, you can become an ethical hacker after B.Tech. You can do courses on Coursera or Udemy related to Ethical Hacking. Then apply for an internship on Internshala. It will be beneficial for you in future endeavours.

There are also universities which have started providing courses related to Ethical Hacking with Computer science as a mainstream.

You can check universities like Chandigarh University, Lovely Profesional University, MIT, Amity University etc.