Tuning Electrical Properties by High Electronegativity Dopant for Ambipolar Zinc Nitride Semiconductor

High-performance complementary metal–oxide–semiconductor (CMOS) integrated devices and circuits are widely used from memory devices to image sensors, logic devices, and switching and driving devices in displays. In the case of silicon-based CMOS, transfer printing technology is essential, which greatly increases the process cost. Therefore, it is necessary to develop NMOS and PMOS fabrication technologies capable of a direct deposition process on a substrate. On the other hand, high-density unipolar p-type and n-type (non-Si based) transistors are each individually fabricated with different semiconductor materials and integrated to form logic circuits. The separation process requirements of circuits further complicate the manufacturing process. In contrast, ambipolar transistors that can implement both p-type and n-type characteristics with a single material, are promising candidates for highly integrated CMOS circuits with effectively simplified designs.<br/>So far, ambipolar semiconductor materials have been mainly reported based on copper nitride or organic/inorganic perovskite. However, copper nitride is not suitable for mass production and commercialization because high-temperature epitaxial growth is required during the deposition process. On the other hand, organic/inorganic perovskite has the advantage of being able to have both n-type and p-type properties as a single material. But, there is a problem that mobility is very low and unstable, so it is easily decomposed in the atmosphere. In order to overcome this limitation, it is necessary to develop a new ambipolar semiconductor material capable of large-scale deposition and excellent electrical properties.<br/>Herein, the nitride-based semiconductor materials fabricated by the sputtering process at room temperature are proposed as the ambipolar semiconductor material, which is advantageous for a large area and mass production. The fluorine (F) which has the high electronegativity can act as an acceptor when incorporated as an interstitial dopant in the Zn₃N₂ matrix. Therefore, both n- and p-type characteristics can be achieved through a single Zn₃N₂ material by controlling the amount of F during the sputtering deposition process. As a result, F-incorporated zinc nitride TFTs exhibited symmetric ambipolar properties with high field-effect mobility. Also, the CMOS-like inverters composed of two Zn₃N₂ ambipolar TFTs has been successfully implemented with excellent voltage gain characteristics. These characteristics offer the applicability to low-cost, large-area and high-efficiency CMOS circuits.