Barrier characteristics of gold Schottky contacts on moderately doped n-InP based on temperature dependent I–V and C–V measurements

The temperature dependences of current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the gold Schottky contacts on moderately doped n-InP (Au/MD n-InP) Schottky barrier diodes (SBDs) have been systematically investigated in the temperature range of 60–300 K. The main diode parameters, ideality factor (n  ) and zero-bias barrier height (apparent barrier height) (Φb0j) were found to be strongly temperature dependent and while the Φb0j decreases, the n   and the (ΦbC) increase with decreasing temperature. According to Thermionic Emission (TE) theory, the slope of the conventional Richardson plot [In(J0/T2) vs. 1000/T] should give the barrier height. However, the experimental data obtained do not correlate well with a straight line below 160 K. This behaviour has been interpreted on the basis of standard TE   theory and the assumption of a Gaussian distribution of the barrier heights due to barrier inhomogeneities that persist at the metal-semiconductor interface. The linearity of the apparent barrier height (Φb0j) vs. 1/(2kT  ) plot that yields a mean barrier height (Φ¯b0j) of 0.526 eV and a standard deviation (σs0) of 0.06 eV, was interpreted as an evidence to apply the Gaussian distribution of the barrier height. Furthermore, modified Richardson plot [In(J0/T2)-(q2σs02/2k2T2) vs. 1/T  ] has a good linearity over the investigated temperature range and gives the Φ¯b0j and the Richardson constant (A∗) values as 0.532 eV and 15.90 AK−2cm−2, respectively. The mean barrier heights obtained from both plots are appropriate with each other and the value of A∗ obtained from the modified Richardson plot is close to the theoretical value of 9.4 AK−2cm−2 for n-InP. From the C–V characteristics, measured at 1 MHz, the capacitance was determined to increase with increasing temperature. C–V measurements have resulted in higher barrier heights than those obtained from I–V measurements. The discrepancy between Schottky barrier heights(SBHs) obtained from I–V and C–V measurements was also interpreted. As a result, it can be concluded that the temperature dependent characteristic parameters for Au/MD n-InP SBDs can be successfully explained on the basis of TE mechanism with Gaussian distribution of the barrier heights.