Understanding the Formation of Midgap States in GaAs(001)-β2(2x4) with Surface Defects Based on Density Functional Theory

摘要

Understanding the defect feature of GaAs(001) in the formation of midgap state is significant in gaining new insights for its applications in efficient photoconductive detection and emission in terahertz (THz) technology. In this work, we investigate the role of surface point defects in the structural and electronic properties of GaAs(001)-β2(2x4) based on density functional theory (DFT). Midgap states were found even on surfaces with high formation energies relative to the clean surface as seen in their band structures. The formation of these states is attributed to the redistribution of charges and supports the observed two-step photon absorption in experiments.