jacbaye

Get yourself an ultrasonic cat deterrent, stick it outside you door so the cat triggers it when it comes near. Unless you have v sensitive ears you won't hear it but the cat will and it should bugger off!
Alternatively get some cat nip and put it somewhere far enough away from your room that the cat is attracted to it instead. Just be careful with that approach though as you may attract other cats which I guess is not what you are after!