Observation of P donors on the Si(111) surface by scanning tunneling microscopy

We report on the individual observation of substitutional P donors on the reconstructed Si (111) 2 × 1 surface by means of scanning tunneling microscopy and tunneling spectroscopy. Depending on the scanning voltage, the dopants give rise to different features superimposed on the background lattice. This is explained by the influence of the charged P atom on the electronic surface-states resulting in a local band shift. The spatial arrangement of the donors obeys a statistical distribution, excluding significant clustering even at a P concentration of 6 × 10 19 cm −3 which is far above the metal-insulator transition.