How to inject the interface only with class string name in the runtime

E.g. have an interface IFoo, know that only one class implements IFoo and the classstring name is "AAAA".  

How to inject this scenario in startup.cs?

Seems like we can do like:

services.AddTransient(typeof(IFoo), Type.GetType("AAAA", fullNameSpace));

But is this the good idea?