Effect of N solubility in the SnO2 host lattice on the structural, electrical, and optical properties of p-type Ga- and N- co-doped SnO2 (GNTO) films

Abstract

To improve the electrical conductivity of SnO2 films co-doped with Ga and N, the incorporation of N into the host lattice should be as high as possible while avoiding the degradation of the crystal structure of the film. In this work, the best electrical properties were found for p-type Ga- and N- co-doped SnO2 films deposited at 400 °C in a mixture of 10 % Ar and 90 % N2 gas from 15 wt% Ga2O3-doped SnO2 targets. The Ga3+-Sn4+ and N3--O2- substitutions were confirmed using X-ray photoelectron analysis, optical transmittance spectroscopy, and X-ray diffraction analysis. The changes of the (101) tetragonal rutile peak to the (111) and (200) cubic lattice plane peaks of SnO2 indicated the successful N3--O2- substitution. The substantial incorporation of N into the SnO2 lattice was found to depend on the Ga3+-Sn4+ substitution. The best electrical properties were achieved for the GNTO-15-90 film, with a resistivity of 0.008 Ω cm, hole concentration of 5.64 × 1019 cm-3, and hole mobility of 13.85 cm2/Vs. The I–V characteristics of p-GNTO-x-y/n-Si heterojunctions under illumination demonstrated that the GNTO-x-y films act as a p-type semiconductor and the photocurrent plots of the p-GNTO-x-y/n-Si heterojunction diodes were highly reproducible.