Synthesis of submillimeter-scale laterally-grown germanium monosulfide thin films and their electro-optic applications

Abstract

Layered two-dimensional Group IV monochalcogenide semiconductors, a novel group of functional materials, are a focus of growing research interest. Numerous reports on germanium monosulfide (GeS) provide evidence of its advanced properties that gives it potential for application in electronics and optoelectronics. However, currently synthesized GeS tends to be patchy and discontinuous. In this study, a novel method that takes Mullins–Sekerka instability into account is proposed to grow continuous GeS thin films. By applying a pre-deposited amorphous GeS layer, submillimeter-scale laterally-grown GeS thin films with single domain areas of 800 μm in size and 100 nm in thickness are successfully achieved. Field-effect transistor (FET) arrays with GeS thin films directly grown on a SiO₂/Si substrate at a growth temperature of 420 °C and isolated GeS channel patterns are fabricated for the first time and show clear gate voltage-dependent current–voltage (I–V) characteristics. We also obtained the hysteresis response of the I–V characteristics, which exhibit notably restrained behavior under light illumination. The successful synthesis of submillimeter-scale laterally-grown GeS thin films and the fabrication of GeS FET arrays should unlock the significant potential of GeS for use as a key functional material in the development of next-generation electronic and optoelectronic applications, such as full-light controlled computing-in-memory devices and sensors.