Area-Dependent Switching in Thin Film-Silicon Devices

We report on the area dependence of switching in both Cr/p ⁺a-Si:H/Ag(Al) and Cr/p⁺μc-Si/Ag(Al) filament switches. The doped amorphous (a-Si:H) or macrocrystalline (μc-Si) thin Si layers are made by hot-wire chemical vapor deposition. The device active region area (A) is varied over 5 orders of magnitude, from 10^-7 to 10^-2 cm², using photo lithographically defined Ag and Al top contacts. Before switching, the resistance of 100-μm² devices is normally about 100 kΩ for μc-Si and 10 GΩ for a-Si:H. After switching with applied current ramps, the resistance decreases to a few hundred ohms in all a-Si devices and to a few thousands ohms in μc-Si devices. In both μc-Si and a-Si:H devices, the switching voltage (V₂) decreases with increasing device area according to V_sw ∼ V ₀-αln(A/A₀) with α=0.3V for a-Si:H and α=0.04V for μc-Si. For both materials, the switching current roughly obeys the power law I_sw ∝ A^β with β∼l. A statistical model is proposed to explain the area scaling of the switching voltage and relate the parameters to the material properties.