Expanded InSe Crystal Structure with Reduced Intrinsic Defects for High-Performance Field-Effect Transistors

Intrinsic defect plays a crucial role in the electrical and photoelectrical performance of InSe-based FETs. Here, a space-growth InSe on China Space Station with reduced intrinsic defects is reported and high-performance InSe field-effect transistors are developed. Spherical aberration corrected transmission electron microscope analysis reveals that the space grown InSe presents lattice expansion of 1.29% along the intralayer direction (a,b plane) and 3.65% along the interlayer direction (c-axis). Density functional theory calculations reveal that the defect generation energy of expanded space InSe is larger than that of ground InSe, improving lattice integrity. The lattice variations in space InSe contribute to unique electronic properties with a narrower bandgap, smaller effective mass of electrons, and increased electronic states near the Fermi level, which reduces carrier scattering and facilitates electron transport. Space InSe FET presents better electrical characteristics (I_on of 6.0 µA µm^-1, on/off ratio of 10⁸ and hysteresis voltage of 0.6 V) and photoelectrical performance (responsivity of 5316 A W^-1 and detectivity of 1.38 × 10¹² Jones) than the ground InSe FET, in which InSe is grown on the ground. This study provides unique insights into the investigation of crystal structure and promotes the development of high-performance 2D FETs.