Layered Zn-Based Semiconductors K2zn3s4 and Rb2zn3se4: Crystal Growth, Structure and Potential P-Type Transparent Conductivity

Exploring semiconductors with a large band gap and a small hole effective mass are of great importance for the development of outstanding p-type transparent conducting materials. In this work, we report the single crystal growth of two Zn-based chalcogenides K2Zn3S4 and Rb2Zn3Se4. Single crystal X-ray diffraction revealed that K2Zn3S4 and Rb2Zn3Se4 crystallize in P2/c and Ibam space group, respectively. Both compounds show layered structure, and the layers are formed by edge-sharing tetragonal [Zn3Q4]2- units and alkalimetal cations are distributed between the layers. To our surprise, compared to the previously reported structure obtained by powder X-ray diffraction, K2Zn3S4 crystallized in a new type of structure in which adjacent layers were displaced. Both experiments and theoretical calculations indicate that K2Zn3S4 and Rb2Zn3Se4 are direct semiconductors with large band gaps, and the experimental values are 3.6 eV for K2Zn3S4 and 3.1 eV for Rb2Zn3Se4. Based on first-principles calculations, the hole effective masses of K2Zn3S4 are calculated to be as small as 0.425 me, revealing the potential remarkable transparent conductivity in this Zn-based chalcogenide.