Temperature Modulating Fermi Level Pinning in 2D GeSe for High-Performance Transistor

2D layered germanium selenide (GeSe) material possesses in-plane anisotropy because of low-symmetry crystal structure with a new degree of freedom for enhanced optical and electronic properties. However, their systematic vibrational and electronics properties are still under the scope to study. Herein, the vibrational properties of GeSe sheets are studied by Raman spectroscopy. Whereas, the temperature-dependent electronic band structure is studied using angle-resolved photoemission spectroscopy (ARPES) combined with density functional theory calculations. Moreover, the field-effect transistor (FET) is fabricated on a few-layer GeSe with high performance. The vibrational modes (Formula presented.) and (Formula presented.) demonstrates linear softening as the temperature increases, with temperature coefficient value associated by anharmonic phonon–phonon/electron coupling. Besides, the enhanced dielectric screening effect of long-range Coulomb and interlayer interaction is observed from bulk to monolayer. Similarly, ARPES results further show Fermi level movement toward the valance band as increased temperature represents hole doping to pining the Fermi level, which indicates superior carrier concentration for electronic properties. The fabricated FET device on six layers GeSe exhibits high carrier mobility of 52.89 cm² V⁻¹ s⁻¹ with an on/off ratio above 4 × 10⁵ at room temperature, while it decreased below the room temperature. Our results provide the important figure of merit for GeSe-based novel nanoelectronic and thermoelectric devices.