chalcogenide perovskite thin films for optoelectronics*

BaZrS₃ belongs to an emerging class of unconventional semiconductor. It is more ionic than conventional compound semiconductors while more covalent than oxide and halide perovskites. Recent publications on powder samples reveal that it has a direct band gap of 1.7-1.8 eV, a high stability against moisture and pressure, and a very strong interaction with light. However, the lack of thin film samples has become the major roadblock in fundamental studies and device applications. Here we report the fabrication of BaZrS₃ thin films, by sulfurization of oxide films deposited by pulsed laser deposition (PLD). We show that films fabricated by this method are n-type with carrier density in the range of 10¹⁹-10²⁰ cm^-3. The Hall mobility ranges from 2.1 to 13.7 cm²/Vs depending on processing temperature. The optical absorption coefficient is greater than 10⁵ cm^-1 at photon energy greater than 1.97 eV. Temperature dependent conductivity measurements suggest shallow donor levels. Although un-optimized, these material parameters suggest that BaZrS₃ thin films are promising for optoelectronic applications.