Publication Date:
2014-09-30
Description:
Potential variations around the grain boundaries (GBs) in antimony (Sb)-doped n-type and boron (B)-doped p-type BaSi 2 epitaxial films on Si(111) were evaluated by Kelvin probe force microscopy. Sb-doped n-BaSi 2 films exhibited positively charged GBs with a downward band bending at the GBs. The average barrier height for holes was approximately 10 meV for an electron concentration n ≈ 10 17 cm −3 . This downward band bending changed to upward band bending when n was increased to n = 1.8 × 10 18 cm −3 . In the B-doped p-BaSi 2 films, the upward band bending was observed for a hole concentration p ≈ 10 18 cm −3 . The average barrier height for electrons decreased from approximately 25 to 15 meV when p was increased from p = 2.7 × 10 18 to p = 4.0 × 10 18 cm −3 . These results are explained under the assumption that the position of the Fermi level E f at GBs depends on the degree of occupancy of defect states at the GBs, while E f approached the bottom of the conduction band or the top of the valence band in the BaSi 2 grain interiors with increasing impurity concentrations. In both cases, such small barrier heights may not deteriorate the carrier transport properties. The electronic structures of impurity-doped BaSi 2 are also discussed using first-principles pseudopotential method to discuss the insertion sites of impurity atoms and clarify the reason for the observed n-type conduction in the Sb-doped BaSi 2 and p-type conduction in the B-doped BaSi 2 .
Print ISSN:
0021-8979
Electronic ISSN:
1089-7550
Topics:
Physics
