Hello Manisha,  

You can do many things after b.tech. After completing the b tech graduation you can choose many things like:

1) If you want to go for further studies you go for post-graduation from various fields like GATE for m.tech, CAT for mba etc. their are many more exams like this. You can also go to foreign to contimue you further studies.

2) Or, you can go for follwing job option too;

• Indian Administrative Service
• Union Public Service Commission of India
• Indian Railways
• Entrepreneurship
• School or College Teacher
• Indian Space Research Organisation (ISRO)
• Defence Research and Development Organisation (DRDO)
• Bharat Sanchar Nigam Limited (BSNL,India )
• Bharat Heavy Electricals Limited
• Bharat Electronics Limited
• Oil and Natural Gas Corporation (ONGC)
• Oil India Limited
• Politics(for eg. Arvind Kejriwal (politician))
• Military Engineering Services, India
• All India Radio

and many more are their. 

Do only that thing in which you are intrested the most.

Hope this helped you!!

Thank you