The Investigation of Current-Conduction Mechanisms of Te/NaF:CdS/SnO2 Structure in Wide Temperature Range of 80–400 K

Abstract

In order to interpret the current-conduction mechanisms of the Te/NaF:CdS/SnO2 structure, current–voltage (I–V) measurements were carried out in the temperature range of 80–400 K. Experimental results show that the main electrical parameters such as reverse-saturation current (I 0 ), ideality factor (n) and zero-bias barrier height (ϕ B0 ) values were found to be strong functions of temperature. The I 0 , n and ϕ B0 values were found as 3.16 × 10−12 A, 17.84 and 0.232 eV at 80 K and 2.85 × 10−7 A, 1.40 and 0.877 eV at 400 K, respectively. Therefore, we have attempted to draw ϕ B0 versus q/2kT plot in order to obtain the evidence of a Gaussian distribution of the barrier heights (BHs) and this plot shows two straight lines with different slopes. From these plots, mean BH $$ \left( {\bar{\phi }_{B0} } \right) = 0.673 $$ eV and zero-bias standard deviation (σ s ) = 0.079 V in the first region (80–170 K), $$ \bar{\phi }_{B0} = 1.279 $$ eV and σ s = 0.160 V in the second region (200–400 K) have been obtained, respectively. The values of Richardson constant (A*) were obtained from the modified Richardson plot as 21.43 A cm−2 K−2 (200–400 K) and 16.07 A cm−2 K−2 (80–170 K), respectively. This 21.43 A cm−2 K−2 value of A* for the first region is in very close agreement with the known theoretical value of 23 A cm−2 K−2 for n-type CdS. It has been concluded that the temperature dependent I–V characteristics of the Te/NaF:CdS/SnO2 structure can be successfully explained by the basis of thermionic emission mechanism with double Gaussian distribution of the BHs rather than other mechanisms.