Large lattice-relaxation-induced intrinsic shallow p-type characteristics in monolayer black phosphorus and black arsenic

Applied Physics Letters, Volume 118, Issue 8, February 2021. Technological application of semiconductors depends critically on their defect properties. Recently, it has been experimentally observed that monolayer (ML) black phosphorus (BP) and black arsenic (BAs) are intrinsic p-type semiconductors, which conflict with the theoretical predictions previously acknowledged that there are no shallow defects in two-dimensional semiconductors. In this paper, we have systematically studied the properties of intrinsic defects in ML BP and BAs using the “transfer to real state” model. We confirmed that both P and As vacancies are shallow dominating acceptors, resulting in the p-type conductivity in ML BP and BAs, respectively. These shallow acceptor levels arise from the symmetry lowering induced by the large local structural distortion for the charged vacancy state. To validate our simulation, we also calculated the hole concentrations that are consistent with the experimentally measured p-type conductivity in both materials. Our results, therefore, help explain the origin of the intrinsic p-type conductivity in ML BP and BAs, which reinforces the comprehension for the defect properties in two-dimensional materials.