Metal-semiconductor (M-S) junctions are prepared in this study by thermal evaporation technique, in which we used indium (In), silver (Ag) and gold (Au) films and aluminum (Al) films. The Al/c-Si/In, Al/c-Si/Ag and Al/c-Si/Au diodes heat treated at different annealing temperatures 303,373 and 473 K. The ohmic contact was aluminum with thickness of about 0.2 µm and the Schottky contacts were indium, silver and gold with thickness of (0.1, 0.2) µm under vacuum conditions of about 10-5 mbar.The effects of annealing temperatures and work functions have been studied by current-voltage and capacitance- voltage characteristics. The I-V characteristics showed that the rectification properties of all prepared diodes were improved with increasing the annealing temperature and the metal work functions (the ideality factor and the saturation current density decreased). The ideality factor (n), saturation current density (Js) and the barrier height (ΦB) were calculated using I-V plots with semilogarithmatic scale.The current–voltage characteristic of Al/c-Si/In, Al/c-Si/Ag and Al/c-Si/Au junctions showed that the current varies approximately exponentially with applied voltage and the junction was coinciding with recombination–tunneling model, the dark current decreases with increase of the thickness. Under illumination, the photocurrent increases and decreases with increase of annealing temperatures and thickness, respectively. The C-V characteristics of Al/c-Si/In and Al/c-Si/Ag diodes have been prepared at different thickness except Al/c-Si/Au at thickness equal to 0.2µm and annealing temperatures. The reverse bias capacitance was measured as a function of bias voltage at frequency 1 MHz; the capacitance decreases with increasing the reverse bias voltage, also with increasing of thickness and annealing temperatures. The built-in voltage (Vbi), barrier height (ΦB) and the carrier concentration (Na) were calculated using Mott-Schottky plot (C-2 vs. V). The d.c. conductivity measurements using Arrhenius plot (lnσ=f(103/T)) showed that there are two activation energies Ea1,Ea2.The electrical activation energies increase with increasing annealing temperatures.
