Distance/Correspondence

After completing your Master;s degree with a minimum of 55%, you need to qualify the tests such as GATE/CSIR-NET/ JEST and TIFR /NEST /SLET, etc. If you qualify the written test, then you'll be called for the interview. In some universities, you'll be required to undergo their separate written test and interview. Ph.D is offered in two modes: Part-Time and Full-Time.
Part-Time: A candidate has to attend classes on weekends. Full-Time: A candidate has to attend regular classes (56 days a week). I am enlisting a few good colleges which are doing really well in this field of research. You can do it from:
Delhi University, University of Hyderabad, Jadavpur University, Jawaharlal Nehru University, Lovely Professional University, Jamia Mililia Islamia University, Banaras Hindu University, Aligarh Muslim University, University of Mumbai, Christ university, MS Ramaiah University, The Maharaj Sayaji Rao University, Anna University and Indira Gandhi National Open University (New Delhi).

In India, no university is offering B.Tech or BE degrees in engineering and technology. This type degrees in distance education has banned by government of India. Up to 2009 JNTU Hyderabad, Andhra university Visakhapatnam Nagarjuna university Guntur Karnataka university Mysore,and IGNOU New Delhi offered this type degrees. and AMIE of institution of engineers Calcutta also offer this type. In this AMIE is only recognized by government of India and no other university in India having the recognition by HRD ministry.
So, please note no university recognized by government of India and UGC. But, this matter is under the consideration of UGC to allow the universities to offer the graduation and post gradation courses in technical education. If you do any such unrecognized courses those will not useful to get any government jobs and not eligible for higher studies. These are just waste of time and money.