Mobility fluctuation Controlled Linear Positive Magnetoresistance in 2D Semiconductor Bi₂O₂Se nano-plates

Bi₂O₂Se is a promising 2D semiconductor with ultrahigh mobility and excellent stability in ambient conditions. We report the observation of positive and linear magnetoresistance in both Se-poor and Se-rich Bi₂O₂Se nano-plates grown by chemical vapor deposition. In Se poor Bi₂O₂Se nano-plates, the pronounced Shubnikov-de Hass oscillations lie in the linear magnetoresistance background. The Se-poor Bi₂O₂Se nano-plates show a typical 2D conduction feature with a small effective mass of 0.032m₀. The average transport Hall mobility, i.e. less than 5500 cm²V^-1s^-1, is significantly reduced, compared to the ultrahigh quantum mobility that is as high as 16260 cm²V^-1s^-1. The spatial mobility fluctuation leads to the linear magnetoresistance, which are strongly supported by inhomogeneity in the scanning near-field microscopy images and Shubnikov-de Hass oscillation analyses. On the contrary, Se-rich Bi₂O₂Se samples with the transport mobility less than 300 cm²V^-1s^-1 show a smaller linear magnetoresistance ratio, which is controlled by the average mobility. Our finding expands the understanding of this 2D semiconductor and explores its potential magnetoresistive device application.