Surface band bending in Al/p-Si:Ag diodes for selective addressing of single deep-levels

We report on a study of surface band bending and deep level characteristics in silver-doped p-type silicon deposited with aluminum thin films. Deep level transient spectroscopy is employed to characterize silver related trap states and emission kinetics. Capacitance–voltage measurements of Al/p-Si and Al/p-Si:Ag Schottky diodes suggest a strong downward band bending (>0.5 eV) from the Si bulk toward the Al/Si interface in the absence of an externally applied voltage. This agrees qualitatively with the surface band bending assessments by x-ray photoelectron spectroscopy in both Si and Si:Ag without Al thin film deposition. However, x-ray photoelectron spectroscopy reveals almost flat Si surface bands following deposition of an ultrathin Al film on the surface. The observed difference in surface band bending is attributed to the different probed depths between the two techniques, combined with the creation of a nanometer scale heavy p+ Si surface layer due to Al–Si interfacial reactions. The results suggest the presence of a potential well embedded below the Si surface, and the implication of such interesting surface band structures on selective charging/discharging of individual Ag-related deep levels is provided in relation to the design of scalable quantum devices in Si.