Model calculation of nitrogen properties in III-IV compounds

We present a semiphenomenological model calculation of the nitrogen-related traps in GaP and related compounds. Working in the one-band–one-site approximation, the complex character of the lowest conduction band is taken into account by using the model density of states previously introduced by Kleiman. In the case of NN pairs in GaP, this results in different series of levels whose energy position depends on structure factors which couple the nitrogen-nitrogen relative positions in real space and the extrema of the conduction band in k space. A tentative identification of these levels is done, in the light of the present calculation, by taking account of the experimentally determined symmetry. A comparison is next performed with recent hydrostatic stress experiments and with the pair dependence of the local-field parameter which splits the ${\Gamma }_8$ bound hole. Concerning isolated nitrogen, the model predicts composition and pressure dependences in very good agreement with experimental results in ${\mathrm{Ga}}_{\mathrm{x}}$ ${\mathrm{In}}_{1\mathrm{-}\mathrm{x}}$P, ${\mathrm{GaAs}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{P}}_{\mathrm{x}}$ or GaAs.