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.

ISSN:0734-211X    

DOI:10.1116/1.584199

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We have used scanning tunneling microscopy to study the behavior of indium on the Si(111)7×7 surface at low‐metal coverages. At sufficiently low densities, In atoms replace Si in the 7×7 adatom positions, preserving the 7×7 structure. In this case the In atoms have a tendency to occupy positions along the edges of the unit cell rather than adjacent to the corner holes. Agglomeration of higher In densities around atomic steps can lead to local areas of √3×√3 reconstruction. Examination of a phase boundary between 7×7 and √3×√3 allows the identification of the bonding site of the In adatoms in the √3×√3 structure as the threefold symmetric site above a second layer Si atom in the surface Si double layer.

ISSN:0734-211X    

DOI:10.1116/1.584200

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Realization of high‐quality inverted interfaces has been thwarted by mutually competing surface kinetic requirements. We report a way out of this dilemma based upon reflection high‐energy diffraction (RHEED) studies of GaAs/AlxGa1−xAs(100) system. Liquid nitrogen mobilities comparable to good GaAs/Al0.3Ga0.7As normal heterojunctions at carrier concentrations ∼5×1011/cm2have been realized in inverted heterojunctions grown on the basis of RHEED suggested conditions and procedures.

ISSN:0734-211X    

DOI:10.1116/1.584201

出版商:American Vacuum Society    

年代:1988

数据来源: AIP