Nitrogen p-type doping in polycrystalline zinc selenide telluride films

Abstract

Nitrogen-doped zinc selenide telluride (N:ZnSe_xTe_1-x) is of interest because it is one of the widest-gap II-VI semiconductors that can still be doped p-type with reasonably high hole concentrations. We sputter deposit N:ZnSe_xTe_1-x films, varying Se/(Se+Te), or x, from 0 to 0.7 and N₂ flow rate from 0.25 to 0.75 sccm. Increasing x from 0 to 0.39 at the optimal N₂ flow rate of 0.5 sccm leads to 1.3 at. % nitrogen incorporation and wurtzite phase stabilization. Such doping and alloying increases hole concentration from 3 • 10¹⁸ cm^-3 to 3 • 10¹⁹ cm^-3, although mobility drops from 0.4 to 0.02 cm² V^-1 s^-1. Our sputtered N:ZnSe_0.38Te_0.62 has an absorption onset 0.1 eV greater than ZnTe. Increasing x from 0 to 0.51 enhances transmittance by moving absorption onset from 1.87 to 2.11 eV with diminished band gap bowing likely due to disorder, and increases the work function from 5.12 to 5.42 eV. This combination of properties makes sputtered N:ZnSe_xTe_1-x desirable for transparent p-type contacts in polycrystalline Cd(Se,Te) optoelectronic devices.