Reversing doping asymmetry in semiconductor thin films with external voltage

Doping asymmetry is a notable phenomenon with semiconductors and a particularly long-standing challenge limiting the applications of most wide band-gap semiconductors, which are inherent of spontaneous heavy nor p-type doping because of their extreme band edges. This study theoretically shows that by applying a proper external voltage on materials during their growth or doping processes, we can largely tune the band edges and consequently reverse the doping asymmetry in semiconductor thin films. We take zinc oxide as a touchstone and computationally demonstrate that this voltage-assisted doping approach efficiently suppresses the spontaneous n-type defects by around four orders under three distinct growth conditions and successfully generates p-type zinc oxide up to the lowest acceptor levels. The proposed approach is insensitive to materials, growth conditions, or defects origins, and thus offers a general solution to the doping asymmetry in semiconductor thin films.