Hi Kartik, hope you are doing well, after completion of your diploma you have two options one is to get into the job and the other is to study further like B.Tech to sharpen your skills further. However, you have interesting jobs to do as you are done with your diploma. Here are some PSU's (Public Sector Companies) where you have the job opportunities for sure.

• GAIL INDIA Ltd.
• BHEL
• COAL INDIA LIMITED
• BEL (Bharat Electronics Limited)
• HPCL
• EIL(Engineering India Limited)
• BPCL (Bharat Petroleum)
• SAIL
• INDIAN OIL
• Power Grid Corporation of India Ltd.
• Railtech Corp. Ltd
  

It's up to you to do the job or study further as both are good in their own domains. 

I think it helps you!!!

Keep Smiling:)

Wish you good luck!:)