M.Tech

Hello Mayank,
It's great to see someone to be interested in M.Tech to get into teaching field.
You should choose as per your interest, skills and capabilities. Also, you should as per where are you willing to work, in India or abroad?
In India as per the preferences most common and popular courses in descending order are thermal, design, industrial and automobile.

For getting admission in M.Tech course in Gujarat, you have to participate in PGCET exam.
Gujarat Post Graduate Common Entrance Test is conducted by the Admission Committee for Professional Courses (ACPC) for the M.Tech/ M.E seats in government, Grant-in aid and self-financed institutes in the state of Gujarat.
Eligibility criteria:
Candidates must clear B.E/B.Tech in their respective disciplines with a minimum of 50% in aggregate (45% for SC/ST/SEBC candidates).
Candidates who have qualified in GATE must apply online and need not appear for the entrance exam.

Both are totally different courses. You need to find out your area of interest. You should select the course as per your stream.

Hi,
According to your query you can consider these options:
Electronic and communication
Wireless
VLSI
Nuclear
Solar