Investigating N solubility in the host lattice of p-type Al- and N- co-doped SnO2 films with various N2 contents in sputtering gas

Abstract

Abstract The Al3+–Sn4+ substitution into p-type Al- and N- co-doped SnO2 films enhances the N solubility in the SnO2 host lattice. The N solubility in the SnO2 host lattice increased with an increase in N2 content in the mixed sputtering gas, and the optimum N2 content was found to be 60 %, which corresponds to high film crystal quality and the lowest resistivity. The Al3+–Sn4+ and N3−–O2− substitution was verified using X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy, energy‐dispersive X‐ray (EDX), and X-ray diffraction (XRD) patterns. The SnO2 tetragonal rutile to cubic phase transformation indicated high N solubility in the SnO2 host lattice, while the Al3+–Sn4+ replacement was also verified by the crystal evolution of a (101) lattice reflection and the occurrence of the charge compensation effect. The best values achieved for resistivity, hole concentration, and hole mobility of the film were 6.4 × 10−3 Ω cm, 6.4 × 1019 cm−3, and 15.2 cm2 V−1 s−1, respectively. The current-voltage characteristics of films/n-Si heterojunctions under the illumination condition showed the p-type conductive properties of the films, and photocurrent response of the optimum film/n-Si heterojunction diode under the illumination condition of monochromatic wavelength light-emitting diodes (LEDs) exhibited a sufficient reproducible cycle and verified the N3−acceptor and VO donor levels in the bandgap.