$ionicPopup, "enter" to submit form

I am using $ionicPopup prompt() and show() to display a popup and gather inputs. I want the user to be able to use the “enter” or “go” keys on the device keyboard (Android & iOS) to submit.

Normally I’d wrap the form and use the submit= tag, but I don’t know how to accomplish this using $ionicPopup

How can I handle form submit functionality tied to a button within an $ionicPopup?

I would use show() to build custom forms in popups.
there you can build up an own html-template with a full form and ng-submit.
If you want to close the popup within this submit function you can take a look in the ionic doc example:
http://ionicframework.com/docs/api/service/$ionicPopup/

You can manually close a popup:
myPopup.close();

after popup creation you get the popup-objekt --> so you can use it in your submit-function