Correlation between carrier recombination and p-type doping in P monodoped and In–P codoped ZnO epilayers

Abstract

The carrier recombination processes in p-type ZnO epilayers with P monodoping and In–P codoping have been studied by temperature-dependent photoluminescence spectroscopy. Good correlations were observed between carrier recombination and acceptor and donor energy levels. The exciton transition feature of acceptor-bound excitons (3.350eV), the free electron-acceptor emission (3.315eV), and the donor-acceptor-pair emission (3.246eV) exhibited different carrier recombination associated various defect complexes. The origins of two broad emissions at ∼2.99 and ∼2.89eV were found to be due to different photoelectron radiative transitions associated with deep level acceptors (isolated Zn vacancies). The acceptor-bound energies for P monodoped and In–P codoped epilayers ∼195 and ∼127meV, respectively. The small binding energy is helpful for acceptor ionization at room temperature, resulting in a high hole concentration in the codoped epilayer.