Electron scattering mechanisms in polycrystalline sputtered zinc tin oxynitride thin films

Abstract

Zinc tin nitride (ZnSnN2) is an emerging ternary nitride semiconductor studied for applications in solar cells, light-emitting diodes, and other optoelectronic devices. For all of these applications, the charge carrier mobility is an important property. However, the dominant electron scattering mechanisms in ZnSnN2 are unclear, especially in the presence of oxygen that is often incorporated during thin film sputter deposition of this material. In addition, there are no experimental reports on the concentration of defects in such polycrystalline sputtered zinc tin oxynitride Zn1+xSn1−xN2−2xO2x (ZTNO) thin films. Here, we address both of these questions using temperature-dependent Hall effect measurements of sputtered ZTNO thin films as a function of Zn composition and O content. The measured temperature dependence of the mobility is fitted to scattering on ionized and neutral defects and to grain boundary scattering. The results indicate that ZTNO is a heavily compensated semiconductor, with a high density of neutral defects dominating the electron scattering processes. First principles theoretical calculations indicate that these neutral defects are likely to originate from the abundant ZnSn−2ON complexes in the ZTNO material. Overall, these results establish the dominant electron scattering mechanisms in polycrystalline sputtered ZTNO and help position this material for future use in optoelectronic devices.