Greetings from the Academy of Saint Gabriel!
You asked us about the name <Phalen> or <Phelan> as a name of Irish origin in the 6th-14th centuries:
This appears to be an American name derived from <O/ Faoláin> . The spelling <Phalen> is unlikely before 1300, but the spellings <Fáelán> or <Faolán> should be fine.
For the middle of the time period you asked about, a name of the form <Fáelán mac X> (where X is the father's name) would be fine, as would a nickname <Fáelán Ruad>, that is "Faelan the Red".
We hope this has been helpful, and that we can continue to assist you.
Arval Benicouer, and Talan Gwynek contributed to this letter.
--Walraven van Nijmegen
Academy of S. Gabriel
 Edward MacLysaght. "The Surnames of Ireland"
Irish Academic Press Ltd., Dublin, 1985.