Electron-Hole Puddles and Carrier Transport for Ultrathin Field-Effect Transistors

Abstract Employing both theoretical modeling and experimental measurements, we investigate the impact of electron-hole puddles on two-dimensional (2D) carrier transport in ultrathin field-effect transistors. The electron-hole puddles are caused by charged impurities that are inevitably present in the device environment. We propose a theoretical model quantifying potential fluctuations induced by residual electric charges and analyze their effects on carrier density and density of states. Combining both Boltzmann transport theory and self-consistent effective-medium theory, the calculated conductivity shows excellent agreement with experimental data from inhomogeneous PtSe 2 systems. Our findings show that electron-hole puddles lead to reduced mobility, threshold gate voltage shifts, and enhanced minimum conductivity, and these effects become particularly pronounced in systems with thin conducting channels. It reveals that the electron-hole puddles play a crucial role near band edges — regions typically characterized by low carrier density where the variations in the local potential induce a complex admixture of electron and hole transport under specific gate biasing. Furthermore, as the layer thickness increases, the potential fluctuations caused by surface impurities diminish, and we identify a transition from inhomogeneous to homogeneous transport. This study provides a comprehensive framework applicable to various 2D material systems, offering valuable insights for optimizing ultrathin electronic devices.