The choice of subjects for doing an MTech depends on your inclinations and also your engineering background. In my opinion, the best bet would be Microelectronics or digital electronics and communication.
Additionally, there is a branch called the School of Information Science (SOIS) that offers a degree equivalent to an MTech degree which is MS. Its course is at or with industrial trends. The overall curriculum focuses more on lab work than theoretical knowledge. The courses offered here are embedded systems and VLSI digital electronics.
In all, MS offers a better hands-on experience but MTech is a better choice if you want to pursue teaching.