The Ultrashallow Thermal Donors in Silicon

The central-cell correction (CCC) is the difference between the ionization energy Ei0 of the donor and the EM value taken as 31.26 meV. The EM value of the 2p i — 2po spacing is 5.09 meV (after [92]) 

A negative value of the central-cell correction indicates a central-cell potential which is repulsive for electrons. 

It must also be mentioned that evidence for USTDs with ionization energies down to 23 mcV has been obtained by low-temperature admittance spectroscopy and thermally-stimulated capacitance measurements in standard CZ silicon samples annealed at 470°C in oxygen ambient for up to 500 h [1], 

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