Barrier characteristics of Cd/p-GaTe Schottky diodes based on I-V-T measurements

The current-voltage (I-V) characteristics of Cd/p-GaTe Schottky barrier diodes were measured in the temperature range 90-330 K. The apparent barrier height and the ideality factor derived by using thermionic emission (TE) theory were found to be strongly temperature dependent. Evaluating forward I-V data reveals a decrease of zero-bias barrier height (Phi(b0)) but an increase of ideality factor (n) with decrease in temperature, and these changes are more pronounced below 150 K. The conventional Richardson plot exhibits nonlinearity below 150 K with the linear portion corresponding to an activation energy of 0.52 eV The value of effective Richardson constant (A*) turns out to be 6.74 x 10(-2) A K-2 cm(-2) against the theoretical value of 119.4 A K-2 cm(-2). It is demonstrated that the findings cannot be explained on the basis of tunnelling and image force lowering effects. Also, the concept of the flat-band barrier height (Phi(b)(f)) fails to account for the temperature dependence of the diode parameters. Finally, it is demonstrated that these anomalies result due to the barrier height inhomogeneities prevailing at the metal-semiconductor interface. The inhomogeneities are considered to have Gaussian distribution with a mean barrier height of Phi(b0) = 0.886 eV and a standard deviation of sigma(s0) = 0.091 eV at zero bias. Furthermore, the mean barrier height and the Richardson constant values were obtained as 0.875 eV and 62.2 A K-2 cm(-2), respectively, by means of the modified Richardson plot, ln(J(0)/T-2) - (q(2) sigma(s0)(2)/2k(2) T-2) versus 1000/T. Hence, it has been concluded that the temperature dependence of the I-V characteristics of the Schottky barrier on p-type GaTe can be successfully explained on the basis of TE mechanism with Gaussian distribution of the barrier heights.