I 've completed B.Tech (Electronics) and MBA (HR). Want to do Ph.D. Which subject is best for Ph.D? Can I do it in Computer Science?

I 've completed B.Tech (Electronics)-74% and MBA (HR)-84%. Want to do Ph.D. I like to study in Canada. Which subject is best for Ph.D? Can I do it in Computer Science? I also have 2 years of work experience in Online Advertising. Please suggest a good university in Canada.