Theory of Dangling Orbital Defects at the <111> Si/SiO2 Interface

We review the experimental and theoretical pictures of the dangling orbital defects at the <111> Si/SiO₂ interface. We show that recent theory agrees in detail with the observed hyperfine and super hyperfine. Also, the estimated level positions obtained from cluster calculations imply that the dangling orbital on the <111> interface is a normal, positive U defect. This is at variance with recent local-density Green’s-function calculations on the dangling orbital in crystalline silicon, that predict that the dangling orbital is a negative U defect. We discuss possible sources of the discrepancy. Finally, calculations on the recently proposed model for the P_b defect involving a three-fold coordinated oxygen atom yield general disagreement with spin resonance data, as well as with electrical measurements. Hence, the original, simple model of a trivalent silicon atom continues to be strongly preferred.