Investigation of donor-acceptor pair luminescence from ZnSe:N epilayers

Low-temperature photoluminescence (PL) due to donor-acceptor pair recombination was monitored in a series of nitrogen-doped ZnSe epilayers grown by molecular beam epitaxy on GaAs substrates. Emission energies were measured for incident power densities ranging from 10−4 to 10 W/cm2 in samples having different nitrogen doping levels. An ionization energy of 50 meV for the “deep” donor in a lightly doped ZnSe:N sample is determined using power dependence data. Heavily nitrogen-doped samples (⩾8×1018 cm−3) provided evidence for a second deeper donor with an ionization energy greater than 100 meV. In addition, we show the importance of accounting for interference effects when identifying the emission peaks in the PL spectra from heavily doped ZnSe:N.