I have been in the HR field for 5 years now. The best topic for a Ph.D. would be "What causes attrition and how to control attrition." All industries are struggling with this problem with no solution. If you can come up with an innovative solution kit, your Ph.D. will be a success.
Misconceptions About Attrition
Salary, work environment, facilities (cab, cafeteria), growth, higher education, and team handling are not the real reasons for attrition. These are just excuses because the best-paid companies with the best facilities and top management also experience attrition.
It's only because the human mind is never stable, and we don't know what we want, so we keep hopping and blaming the company, salary, growth, politics, etc.
Exploring Solutions
All the above factors may be part of the reason for attrition. Just work around it and do some case studies in the IT/ITES industries.
If you can find a solution, you can even become a Management Guru.