As many IITs are calling for PhD after B.Tech and students who appeared for GATE and could not make it to M.Tech in IITs usually called for PhD exam and interview.
A letter from IIT can make you or anyone think about that program. Here in this post I would like to tell all the pros and cons of this.

The biggest advantage of doing PhD right after of B.Tech is you get to see IITs with not very high score and have a chance to study with highly competitive students. You can also prove to be better than them with hard work and determination.

If you have long term plan for research then this could be a wonderful opportunity. Most of the students are worried about PhD pressure and research aptitude right after B.Tech or BE, I think this will not be an issue. The reason for this is that, one need to take up a bunch of subjects before they start the actual research. These subjects are usually recommend by ones guide and useful in research and also help you to build a solid base to start working. The number of subjects, usually, are same as M.Tech and sometimes professor may ask you to take additional class too.

If you looking for an industry job right after your studies, I think you need to think again about PhD program. A doctorate degree may help you to secure a position in some research lab but finding an industry job is not easy. I was exceptionally lucky in this case because I came to Samsung electronics in Korea in summer internship and they right away offered me a job while leaving. So It was my decision to join or not. I liked teaching, therefore joined Indian Statistical Institute Kolkota for certain amount time too.

The time duration for PhD is also not well defined and may differ from lab to lab or research area. Usually it is something around 4~5 years. During this time one need to be self motivated and stay focused. Always try to have at least one research paper in top most journal of your area of interest.

Most of the PhD students would go abroad for post doctoral research or join as faculty in some college, university or institute based on there quality of research. Few take up the challenges and luck support them to join industry and they choose their career from there. Getting an industry position especially in research is not easy as there are limited laboratories and requirements are too low, as the people who are working as researchers usually don’t move frequently.

To summarize, if you are patient, have really long term plans, self motivated and willing to work for future then you should knock the doors of IITs for PhD. If you are not very patient with books, long reading hours, and would like to complete studies as soon as possible then I would recommend you to try hard to get into to M.Tech in good universities to based on your scores.