Twitter Inc. cofounder Jack Dorsey came to Cambridge Monday on a recruitment drive. He is looking to lure a few Massachusetts Institute of Technology graduates back to California to help him quickly grow his latest innovation: a mobile payments company called Square Inc.

The three-year-old start-up is already one of the early leaders in the fast-growing “mobile wallet” marketplace, which includes tech giants such as Google Inc. and local upstarts like Scvngr, to let consumers make purchases with their smartphones instead of using cash or credit cards.