Thick p-type Mg2Si film on Si: Growth, structure and transport properties

Abstract

A ∼ 0.8–0.9 µm thick Mg₂Si film was grown by pulsed deposition of Mg on Si(111) at 340 °C in UHV. The X-Ray Diffraction (XRD) and cross-sectional High-resolution Transmission Electron Microscopy (x-HRTEM) data demonstrate the high crystal quality and nearly 100% texture of the film. Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS) depth profiling show that the synthesized Mg₂Si contains some oxygen. Hall measurements reveal the p-type conductivity of 130 S/cm and carrier concentration of 6 × 10¹⁸ cm⁻³ at room temperature (RT), the acceptor concentration of ∼ 1.4 × 10¹⁸ cm⁻³ at 190 K, hole activation energy E_a ≈ 26 meV, mobility μ∼5050 cm²/V∙s at 75 K and μ∼134 cm²/V∙s at RT. The p-type conductivity is related to either unintentional doping with oxygen or/and Mg vacancies occurred during the non-equilibrium process of silicide ultra-fast formation. The outstanding transport parameters of the film are explained by its high crystal quality and texture. The films with such thickness and transport properties are suitable for photovoltaic and thermoelectric applications.