All of them are correct. The primary placement of the adverb "already" is after the auxiliary "have". Using "already" at the end of the sentence is also correct, but would be heard as something that is used less frequently, because it is not the normal neutral.
The same goes for "I've
already finished my work", and "I've
finished my work already". The primary placement for "already" is after the subject. A secondary placement would be at the end of a clause or sentence. Both are correct.