High‐Mobility and Air‐Stable Amorphous Semiconductor Composed of Earth‐Abundant Elements: Amorphous Zinc Oxysulfide

Amorphous oxide semiconductors have been widely studied as key materials for flat panel displays and flexible electronics devices. Recently, it has been reported that an amorphous mixed‐anion semiconductor consisting of only earth‐abundant elements, zinc oxynitride, shows high electron mobility and good performance as the channel layer of a thin‐film transistor. However, amorphous zinc oxynitrides are unstable in air. It is demonstrated that another type of earth‐abundant amorphous mixed‐anion semiconductor, amorphous zinc oxysulfide (a‐ZnOxSy) thin film, exhibits electron mobilities comparable to those of conventional amorphous oxide semiconductors, in addition to good chemical stability under ambient conditions. a‐ZnOxSy thin films with a wide compositional range are fabricated through pulsed laser deposition, by alternately depositing ZnO and ZnS. Their transport properties can be controlled by adjusting the laser fluence and anion composition, and conductive a‐ZnOxSy thin films (≈0.30 ≤ y/(x + y) ≤ ≈0.35) show high electron Hall mobilities of 10–15 cm2 V−1 s−1 at a carrier density of < ≈1018 cm−3. Furthermore, the Hall mobility can be maintained in air for at least 12 months. An a‐ZnOxSy thin‐film transistor with a bottom‐gate and top contact configuration shows clear field effect transistor behavior, although its performance is so far moderate. An earth‐abundant amorphous mixed‐anion semiconductor, amorphous zinc oxysulfide (a‐ZnOxSy) thin film, exhibits high electron Hall mobilities comparable to those of conventional amorphous oxide semiconductors (10–15 cm2 V−1 s−1) at a low carrier density (< ≈1018 cm−3). Furthermore, the Hall mobility of a‐ZnOxSy can be maintained in air for at least 12 months, demonstrating its chemical stability.