yes you can take admission in Btech degree in electronics engineering.Doing  b.tech after diploma in mechanical engineering is one of the best option.You can get lateral entry in B.tech through leet which  spans over a periodof 3 years.

Hello Praveen,
Definitely you can take admission in Electronics Engineering. Your admission will be easy if you go for AKTU, Lucknow affiliated engineering colleges. You can take direct admission in 2nd year of engineering through lateral engineering entrance scheme.
Note- not every college take admission through lateral engineering or they don't give choice for branch change.
Good Luck.