Defects at Ge/oxide and III–V/oxide interfaces

Abstract

Display Omitted We use density functional theory to study defects at semiconductor/oxide interfaces.For Ge, we find that dangling bonds are always negatively charged.In HfO2 and ZrO2, cation vacancies and oxygen interstitials are likely to occur.Oxygen vacancies in Al2O3 may act as carrier traps. Using first-principles calculations based on density functional theory, we investigate the impact of defects near interfaces of semiconductor channel materials and oxide dielectrics. We determine defect formation energies and transition levels, paying special attention to an accurate description of electronic structure by employing a hybrid functional. This methodology overcomes the band-gap problem inherent in traditional functionals and renders the approach more predictive. By calculating band alignments between the semiconductor material and the dielectric oxide, we are able to determine the position of defect levels in the oxide relative to the semiconductor band gap and assess how they will affect the device performance. We discuss results for vacancies in Ge, and for point defects in HfO2, ZrO2, and Al2O3. In addition to point defects, we have also investigated the properties of dangling bonds in Ge and Al2O3, which are likely to form in amorphous oxides as well as at semiconductor/oxide interfaces.