They may have done as far as they themselves are concerned, but as they are so ridiculously easy to fake, the answer has to be no.
I am really interested in the subject and I'm a professional photographer. I'm familiar with all the famous "ghost photos" but there isn't a single one that you couldn't mock up in photoshop in 10 minutes.
Ghost do exist though.
Anything can be faked as I said, but these apparently were produced under controlled conditions.You will have to dig a bit further down on that page to find more info about the scientific controls that they went through, but its pretty convincing stuff and the experiment has never been successfully debunked by anyone.