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Photoemission study of GeAs(2̄01): A model for the As‐stabilized Ge surface on GaAs/Ge heterojunctions

 

作者: F. Stucki,   G. J. Lapeyre,   Robert S. Bauer,   P. Zurcher,   J. C. Mikkelsen,  

 

期刊: Journal of Vacuum Science&Technology B: Microelectronics Processing and Phenomena  (AIP Available online 1983)
卷期: Volume 1, issue 4  

页码: 865-870

 

ISSN:0734-211X

 

年代: 1983

 

DOI:10.1116/1.582707

 

出版商: American Vacuum Society

 

关键词: germanium arsenides;photoemission;germanium;gallium arsenides;energy spectra;photoelectron spectroscopy;layered materials;excitation;electronic structure;conduction bands;valence bands;core levels;molecular beam epitaxy;heterojunctions;coatings

 

数据来源: AIP

 

摘要:

We present a study of the electronic states of GeAs as a model for the ordered, anion‐stabilized surface phases which form on Ge when it is grown epitaxially on GaAs substrates using MBE. Angle‐resolved, normal emission photoelectron energy distribution curves for four different azimuthal orientations of the GeAs(2̄01) face (i.e., four different polarizations) have been measured using photon energies fromhν=10 to 28 eV. The valence band structure plots (binding energy versus photon energy) show behavior typical of a layered compound. A large number of valence band states (about 12) are observed, and they show essentially nohν dispersion in normal emission and very little dispersion with polar angle. The electronic states are therefore localized both within and normal to the layer. The excitation of the Ge 3dand the As 3dcore levels into conduction band states observed by measuring the core hole decay emission does not show any enhancement peaks as usually observed if empty surface states exist in the conduction band. This suggests that the GeAs(2̄01) surface may not have any surface states. Chemical bonding information was obtained by measuring the Ge 3dcore level binding energy. The Ge is more tightly bound compared to the bulk Ge as indicated by a 3dcore level chemical shift of 0.45±0.1 eV toward higher binding energy. 3dcore threshold emission for both the Ge and the As is used together with the line shape of the valence band edge emission to determine a forbidden band gap is 0.4±0.3 eV. These results support the Bauer/Mikkelsen hypothesis that the Ge:As surface phase that floats on top of the MBE GaAs/Ge heterojunction is energetically more favorable than the corresponding clean Ge surface having unsatisfied dangling bonds. The data on GeAs(2̄01) leads to a picture of an As‐terminated surface having highly directional oribtals and very low reactivity.

 

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