iPhone 6S Plus' recording audio -- mono or stereo?

When I record audio on iPhone 6S Plus, is it mono or stereo? If it's mono and I use a stereo external mic to record, say from Rode, will the audio be stereo or mono? If it's stereo, can anyone recommend a stereo directional mic. I need it to make short films, and pleasant audio is of utmost importance in movies. The iPhone audio is unprofessional.😕

Cheers!

James