Hi Lynn,
Here a nice thread about your question from Andrea that was posted about 9 months ago.
http://agoracom.com/ir/POETTechnologies/forums/discussion/topics/581162-enough-gallium-and-arsenic-available/?message_id=1823222#message_1823222
If you read it in threaded view you can get all the responses
In short, most of the gallium used today is recycled from scrap. I'm sure the amount required will result in the need to mine more, but like fairchij said most of the virgin Ga is collected as a biproduct of Zn and Al mining operations. Gold Canyon has a property that was investigated for a pure Gallium mining operation, but was apparently not feasible for the demand at the time. Might be worth another look in a year or so :)
As for Arsenic, it could see a bit of a squeeze. But again, the number of chips is reduced with POET and basically everywhere that POET is most useful already depends on a GaAs chip to do part of the work. So POET would add functionality to that chip to make it do *all* of the work, and do orders of magnitude better!