On the Possibility of p-Type Doping in BaSnO₃

The discovery of a p-type transparent conductor would revolutionise optoelectronic devices by enabling fully transparent p-n junctions. Of particular interest are fully transparent homojunctions, which would greatly simplify the manufacturing process and potentially aid device performance. Recent work¹ has produced transparent p-n junctions from BaSnO₃, but the p-type behaviour of the compound has thus far been overlooked in the literature.

Here we seek to understand the defect and transport behaviour of p-type BaSnO₃ using hybrid density functional theory (DFT).² Group 1 metals Li, Na and K and group 13 metals Al, Ga and In are assessed as extrinsic p-type dopants on the Ba and Sn sites, respectively. We find that K and In are the most promising dopants, reaching concentrations of up to 4.7x10¹⁶ cm^-3 and 1.6x10¹⁹ cm^-3 respectively. Both, however, are compensated by low energy O vacancies, limiting the hole carrier concentrations to 5.2x10¹⁴ cm^-3 and 9.8x10¹⁵ cm^-3 respectively. Such high defect concentrations also severely limit the electronic transport, with room temperature mobilities of 5.96 cm² V^-1 s^-1 and 1.27 cm² V^-1 s^-1 respectively. While this does not reach the levels seen in n-type transparent conductors, it does guide the way towards the higher doping concentrations than have so far been achieved experimentally.

[1] Kim, H. M. et al., APL Mater., 2016, 4, 056105.
[2] Willis, J. et al., Appl. Phys. Lett., 2023, accepted.