The best approach for Scrum Teams to produce valuable Increments is to be accountable for developing functionality from beginning to end, as this enables them to deliver potentially releasable products that meet the definition of "Done". The Scrum Guide states that "The Developers are the people in the Scrum Team that are committed to creating any aspect of a usable Increment each Sprint."1 This means that the Developers are not limited by the boundaries of components, layers, or technologies, but rather they collaborate and coordinate to deliver a complete and integrated product that satisfies the Sprint Goal and the Product Owner's expectations.
Reference:
1: The Scrum Guide2, page 7
2: The Scrum Guide