Hey Ravi, 

Since Mechatronics is a very vast field of engineering and is an integrated field so have many options for masters.

You can do post-graduation (Masters) in following fields after B.Tech Mechatronics :

• Mechatronics 
• Robotics
• Automation
• Bio- Mechatronics
• Control Systems 
• Hydraulic and Pneumatic Systems
• Mechatronics Systems

Good Luck!