Dopant activation energy and hole effective mass in heavily Zn-Doped InP

Heavily doped InP epitaxial layers were investigated using variable-temperature van der Pauw and photoluminescence spectroscopy measurements. A quantitative analysis of the electronic properties of the p-type layers was performed to determine the activation energy of Zn as an acceptor as well as total acceptor and donor concentrations. The doping-concentration dependence of the activation energy was discussed in terms of merging of the excited acceptor states with the valence band. The activation energy of the acceptor state for dilute Zn concentrations was determined to be 52 ± 1 meV. A temperature and concentration-dependent density-of-states hole effective mass is proposed to fit the measured hole-concentration curves in the temperature range between 77 and 300K. To explain a hole-concentration saturation effect, the model of incorporation of Zn as an interstitial donor is discussed.