Please help: what documents are needed in order to file EB2 PERM

I am a US PhD with over 3 years of full time working experience in the same field. My employer is filing LC for me. If I want them to file my LC as EB2 PERM, what are the requirements and what kind of documents should I provide? Do I need to ask someones writing me several recommendation letters such as those for NIW cases to help the officer to justify the "exceptional capability" requirement? I appreciate your kind considerations and anxieously look forward your advises. Any information regarding this matter is highly appreciate it.