Scanning tunneling spectroscopy of oxygen adsorbates on the GaAs(110) surface
作者:
Joseph A. Stroscio,
R. M. Feenstra,
期刊:
Journal of Vacuum Science&Technology B: Microelectronics Processing and Phenomena
(AIP Available online 1988)
卷期:
Volume 6,
issue 4
页码: 1472-1478
ISSN:0734-211X
年代: 1988
DOI:10.1116/1.584199
出版商: American Vacuum Society
关键词: OXYGEN;GALLIUM ARSENIDES;ADSORPTION;IMPURITY STATES;SURFACE STRUCTURE;SORPTIVE PROPERTIES;DEPLETION LAYERS;GaAs
数据来源: AIP
摘要:
Spatially resolved measurements of the tunneling current versus applied voltage are obtained for oxygen adsorbed on the GaAs(110) surface, using a scanning tunneling microscopy (STM). Effects with different length scales are observed, arising from two sources of charge in the system: negatively charged adsorbates and a positively charged space charge layer. The space charge layer produces band bending onn‐type material, which is observed as a shift in the onsets for tunneling out of and into the valence and conduction bands, respectively. We analyze these shifts using theoretical calculations of the tunneling current through surface space charge layers. Directly above an oxygen adsorbate onn‐type material, an enhancement in tunneling is observed near the top of the valence band edge, while a corresponding decrease is observed near the bottom of the conduction band. This local behavior is identified as arising from changes is the surface density‐of‐states produced by the Coulomb potential of the charged adsorbate. Onp‐type material, no band bending is observed, and the STM images are indicative of neutral adsorbates. This difference between thenandp‐type results is attributed to the existence of acceptor states in the band gap.
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