Specific contact resistance and carrier tunneling properties of the silver metal/porous silicon/p-Si ohmic contact structure

The ohmic properties of the Ag metal/porous silicon/p-type silicon (Ag metal/PS/p-Si) contact structure have been investigated by measuring the specific contact resistance (rho(c)) and current-voltage (I-V) characteristics, respectively. The characterization of the rho(c) of the contact structure by the extrapolation technique based on the three-point probe (TPP) method shows that the ohmic properties of the resultant contact structure are excellent with rho(c) congruent to 1.01 x 10(-6) Omega cm(2). The relationship between the specific contact resistance and impurity doping level is also discussed. The tunneling theory for the heavily doped semiconductor surface is used to explain the ohmic behavior of the contact structure. The carrier injection properties of the contact structure were examined by measuring the I-V curves as a function of temperature. It shows that under low forward bias voltages, the I-V curves is exhibiting a slight curvature at the origin which indicates that the current transport mechanism is determined by the space charge limited currents or field-induced tunneling process across the potential barrier at the Ag metal/porous silicon interface. The carrier injection across the Schottky potential barrier is used to explain the observed current transport mechanism of the contact structure. (C) 2008 Elsevier B.V. All rights reserved.