Electron trap states at InGaAs/oxide interfaces under inversion through constant Fermi-level ab initio molecular dynamics

We employ constant-Fermi-level ab initio molecular dynamics to investigate defects at the InGaAs/oxide interface upon inversion. We adopt a substoichiometric amorphous model for modelling the structure at the interface and investigate the formation of defect structures upon setting the Fermi-level above the conduction band minimum. The defect formation is detected through both an analysis of the atomic structure and a Wannier-decomposition of the electronic structure. This computer driven approach is able to retrieve In and Ga lone-pair defects and As–As dimer/dangling bond defects, in agreement with previous studies based on physical intuition. In addition, the present simulation reveals hitherto unidentified defect structures consisting of metallic In–In, In–Ga, and Ga–Ga bonds. The defect charge transition levels of such metallic bonds in Al₂O₃ are then determined through a hybrid functional scheme and found to be consistent with the defect density measured at InGaAs/Al₂O₃ interfaces. Hence, we conclude that both In and Ga lone pairs dangling bonds and metallic In–In bonds are valid candidate defects for charge trapping at InGaAs/oxide interfaces upon charge carier inversion. This study demonstrates the effectiveness of constant-Fermi-level ab initio molecular dynamics in revealing and identifying defects at InGaAs/oxide interfaces. (paper)