Physical properties of Zn-Sn-N films governed by the Zn/(Zn + Sn) ratio

Abstract

At present, the application of ZnSnN2 as an active layer in optoelectronic devices is dramatically limited due to its high carrier concentration. It is suggested that off-stoichiometry of cations might be a promising cure. In this work, Zn-Sn-N films with 0.60, 0.67, and 0.85 Zn/(Zn + Sn) ratios were, respectively, fabricated by DC magnetron sputtering. In spite of off-stoichiometry, the films all exhibited a cation-disordered wurtzitelike ZnSnN2 dominated phase except that the crystallinity was decreased with an increasing Zn/(Zn + Sn) ratio. In agreement with the cation-disordered structure, all the Zn-Sn-N films illustrated Raman spectra of a phonon-glasslike characteristic. The refractive index of the films was increased with the Zn/(Zn + Sn) ratio over a wide wavelength range, for example, from 1.990 to 2.459 at the wavelength of 500 nm. The direct optical bandgap of the films varied from 1.36 to 1.68 eV. Most strikingly, an electron concentration of magnitude down to 1016 cm−3 and a very low resistivity down to 10−2 Ω cm were reached for 0.67 and 0.85 Zn/(Zn + Sn) films, respectively. It is highly desirable that both semiconducting and conducting characteristics can be achieved in the Zn-Sn-N material system, which is highly beneficial to its applications in various optoelectronic devices.