Role of dimensionality and quantum confinement in p-type semiconductor indium phosphide quantum dots

We characterize the impurity state responsible for current flow in zinc-doped indium phosphide nanocrystals through first-principles calculations based on a real-space implementation of density-functional theory and pseudopotentials. We found the activation energy of the acceptor state to range from the value of the acceptor state in the bulk (0.03 eV) to up to values of similar to 2.5 eV in the smaller nanocrystals as a result of the three-dimensional quantum confinement. This maximum value for the nanocrystals is an order of magnitude bigger than the maximum value found for one-dimensional nanomaterials (nanowires) within the same theoretical approach (similar to 0.2 eV). Our results show that the progressive reduced dimensionality in p-type indium phosphide materials strongly reduces the capability of the materials to generate free carriers.