Selective area regrowth involves many important topics in materials science, including regrowth dynamics, the impurities at the regrowth interface, field assisted tunneling, electron holography for interface electrostatic potential profile, and dopant profiling. These most recent results in the last three years can be very beneficial for the study of regrowth, interfaces, impurities, and leakage in the GaN materials community and help boost the understanding of selective area regrowth in GaN semiconductors. In this paper, we review challenges and the recent progress for selective area regrowth and doping to realize laterally patterned p-n junctions for vertical GaN power devices, which represents the first comprehensive review on selective area doping in wide bandgap semiconductors.