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

Abstract

Abstract 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‐ZnO x S y ) thin film, exhibits electron mobilities comparable to those of conventional amorphous oxide semiconductors, in addition to good chemical stability under ambient conditions. a‐ZnO x S y 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‐ZnO x S y thin films (≈0.30 ≤ y /( x + y ) ≤ ≈0.35) show high electron Hall mobilities of 10–15 cm 2 V −1 s −1 at a carrier density of < ≈10 18 cm −3 . Furthermore, the Hall mobility can be maintained in air for at least 12 months. An a‐ZnO x S y thin‐film transistor with a bottom‐gate and top contact configuration shows clear field effect transistor behavior, although its performance is so far moderate.