How to approach my might-be-future boss?

hi

After a few years in QA in this company, I'd like to move forward to R&D team (in the same company).

I'd need to approach the R&D manager and let him know that I'd like to join his team,

and also my QA manager and tell him that I wanna move forward to one of the R&D teams.

Do you think that it is better to approach first the R&D manager, have an "unofficial" conversation with him, and tell him that I'd like to join his team?

How should I approach him?

I mean, should I call him and ask to talk to him?

Should I mention on the phone that its about me wanting to apply to join his team?

Thank you guys.