GaAs: Gap state passivation at interfaces and surfaces

Electronic structure calculations on surface, interface and defect configurations of GaAs describe passivation of gap states within the electron counting rule. We find that the critical defects are As-As dimers, which follow chemical trends and give gap states at GaAs-oxide interfaces because they are 4-fold not 3-fold coordinated as they are on surfaces. GaAs interface defects cannot easily be passivated independently.