Tuning surface band bending in transition metal-doped silicon for quantum defect selection

We report a comprehensive study of surface band bending and deep-level characteristics in silver-doped p-type silicon incorporating aluminum thin films. Deep-Level Transient Spectroscopy (DLTS) was employed to characterize Ag-related trap states, revealing distinct emission kinetics indicative of multiple deep centers. Complementary capacitance–voltage (C–V) profiling of Al/p-Si Schottky diodes shows a downward bending of the Si valence band toward the Al/Si interface. In contrast, X-ray Photoelectron Spectroscopy (XPS) indicates a nearly flat band condition a few nanometers below the surface, attributed to a heavily doped p+ Si layer formed through Al–Si interfacial reactions. This depth-dependent variation in band bending suggests a subsurface potential well that modulates carrier capture and emission processes associated with transition-metal-induced deep levels. The implications of this band structure on selective defect charging are discussed in the context of designing Si-based platforms for emerging quantum and optoelectronic applications. Ongoing studies on Ti-doped Si, motivated by recent predictions of Ti color centers, further expand this framework toward Si-integrated photonics in the telecommunication regime.