Achieving p-type conductivity in wide-bandgap SnO2 by a two-step process.

Wide bandgap SnO₂ usually shows n-type conductivity due to intrinsic defects. Herein, we demonstrate the achievement of p-type conduction in SnO₂ with a two-step process, in which 3.3 at. % Mg-doped SnO₂ epitaxial films were first grown on c-Al₂O₃ by pulsed laser deposition and then annealed in an oxygen atmosphere at proper temperature and time. An activation energy of around 85 meV revealed by temperature-dependent resistance measurements verifies Mg as a shallow acceptor in the p-type doping of SnO₂. The post-annealing treatment at suitable temperature and time was found to be crucial to greatly enhance the p-type conductivity of Mg-SnO₂ by removing the interstitial Mg while maintaining the substitutional Mg in the SnO₂ lattice. A hole concentration of 1.43 × 10¹⁷ cm⁻³ and a hole mobility of 4 cm² V⁻¹ s⁻¹ as determined by Hall-effect measurements were achieved for a sample annealed at optimized conditions of 600 °C and 0.5 h. The achievement of high-quality p-type Mg-SnO₂ epitaxial films demonstrates high potential in developing advanced optoelectronic devices based on p-n junctions of SnO₂. [ABSTRACT FROM AUTHOR]