Influence of Surface Chemical Modification on Charge Transport Properties in Ultrathin Silicon Membranes

Abstract

Ultrathin silicon-on-insulator, composed of a crystalline sheet of silicon bounded by native oxide and a buried oxide layer, is extremely resistive because of charge trapping at the interfaces between the sheet of silicon and the oxide. After chemical modification of the top surface with hydrofluoric acid (HF), the sheet resistance drops to values below what is expected based on bulk doping alone. We explain this behavior in terms of surface-induced band structure changes combined with the effective isolation from bulk properties created by crystal thinness.

Integrated freestanding single-crystal silicon nanowires: conductivity and surface treatment

“…The M-S-M model [23,24] applied to fit the data in figure 5 shows twofold lower carrier mobility than the annealed case [20]. The lower effective mobile-carrier density and mobility may explain the discrepancy between our work and [26], where the electrical contacts are Ohmic.…”

“…The inversion of carriers has been observed in HF treated ultrathin silicon membranes [26] and is also a result of bulk studies [26][27][28][29][30]. The inversion of electronic conduction from p-type to n-type depending on the surface condition of the SiNW can be described by Fermi energy pinning [31,32] as we will discuss later.…”

“…The lowered conductivity in the H-terminated SiNW, in contrast to the behavior on SiNMs, for which the conductivity dramatically increases, may be explainable in the following way. An electron carrier concentration of the order of 1.3 × 10 14 cm -3 near the Si surface of the HF treated thin Si membrane due to the Fermi energy pinning has been reported [26,31,32]. In [26], only one side is HF treated.…”

“…An electron carrier concentration of the order of 1.3 × 10 14 cm -3 near the Si surface of the HF treated thin Si membrane due to the Fermi energy pinning has been reported [26,31,32]. In [26], only one side is HF treated. Our SiNW has all four sides H-terminated with the method used in [26].…”

“…In [26], only one side is HF treated. Our SiNW has all four sides H-terminated with the method used in [26]. Because the Debye length is ∼130 nm, the induced electrons may be located throughout the volume of the SiNW.…”