Well, I think it's just matter of English translation. Those two are completely different expressions in Japanese. Let me give you some example. わたしは　アメリカに　きたばかりです。 I have just come to the US. ドアが　あけてある。 The door is opened(by someone). = Someone has opened the door (and it's still open). In the case of "bakari," the subject("watashi" in above example) just has done something. On the other hand, "tearu" describes current state of being of something(subject-"door" in above example) caused by someone not mentioned. So it can be translated like "...has done." in English. Hope it helps! Please just tell me if you need some more explanation.