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

Abstract

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) ( Φ b 0 j ) were found to be strongly temperature dependent and while the Φ b 0 j decreases, the n and the ( Φ b C ) increase with decreasing temperature. According to Thermionic Emission ( TE) theory, the slope of the conventional Richardson plot [ In( J 0/ T 2) 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 ( Φ b 0 j ) vs. 1/(2 kT) plot that yields a mean barrier height ( Φ ¯ b 0 j ) of 0.526 eV and a standard deviation ( σ s0) of 0.06 eV, was interpreted as an evidence to apply the Gaussian distribution of the barrier height. Furthermore, modified Richardson plot [ In ( J 0 / T 2 ) - ( q 2 σ s 0 2 / 2 k 2 T 2 ) vs. 1/ T] has a good linearity over the investigated temperature range and gives the Φ ¯ b 0 j 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.