(a) STM topography of a single donor (bright spot). (b) Distance r dependence of LDOS from a single donor. Energy positions 1`3 give bound state levels. (c) Spatial LDOS maps at 1`3. (d) LDOS intensity of the lowest energy level 1 as a function of distance r. By measuring this dependence, the Bohr radius (aB1) is determined.
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Direct Measurement of the Binding Energy and Bohr Radius of a Single Hydrogenic Defect in a Semiconductor Quantum Well

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@It is well known that the behavior of donor impurities, which are very important for semiconductor devices, can be approximately understood by the hydrogenic model. The two fundamental properties are the binding energy and the Bohr radius. However, These values have not been characterized for a single donor before. By measuring the local density of states (LDOS) in the vicinity of the defect at the semiconductor quantum well surface using low-temperature scanning tunneling microscopy (STM), we have succeeded in determining both the binding energy and the Bohr radius. (Page 28)


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