Interface formation of GaAs with Si(100), Si(111), and Ge(111): core-level spectroscopy for monolayer coverages of GaAs, Ga, and As

The interface structure of thin overlayers of GaAs grown using molecular-beam epitaxy techniques on on-axis Si(100), Si(111), and Ge(111) substrates has been studied using photoemission core-level spectroscopy. Results for As and Ga overlayers are also reported and are utilized to interpret the results for GaAs growth. The interface bonding is found to be the same for growth using predeposition of Ga as for predeposition of As. For GaAs on Si(111), the bonding at the interface is found to consist predominantly of Si-As bonds. We also find strong evidence of island formation before the completion of the first GaAs bilayer. The total area between islands can be reduced either by faster deposition rates or by using a Ga prelayer. For GaAs on Si(100), bonding takes place to both Ga and As but with fewer Si-Ga bonds than Si-As bonds. The tendency to island formation is less than for the Si(111) case. These results are compared with earlier data for As interaction with off-axis Si(100) surfaces to explain the absence of antiphase domains in GaAs grown on off-axis (100) substrates. Roughly equal numbers of Ge-As and Ge-Ga bonds were found for GaAs on Ge(111), and this result is interpreted as indicating that Ge interdiffuses more rapidly into GaAs than does Si.