Nov 5, 2014

Study of barrier inhomogeneities using I–V–T characteristics of Mo/4H–SiC Schottky diode

In the present work we investigate the forward current–voltage (I–V  ) characteristics, over a wide temperature range 298–498 K, of Mo/4H–SiC Schottky diode for which aluminum ion implantation was used to create the high resistivity layer forming the guard ring. The (I–V  ) analysis based on Thermionic Emission (TE) theory shows a decrease of the barrier height ϕ  B and an increase of the ideality factor n   when the temperature decreases. These anomalies are mainly due to the barrier height inhomogeneities at the metal/semiconductor interface as we get a Gaussian distribution of the barrier heights when we plot the apparent barrier height ϕ  ap versus q  /2kT  . The mean barrier height and the standard deviation obtained values are View the MathML sourceB0=1.160 eV and σ0=88.049 mV, respectively.
However, by means of the modified Richardson plot View the MathML source versus q  /kT  , the mean barrier height and the Richardson constant values obtained are View the MathML sourceB0=1.139 eV and A  *=129.425 A/cm2 K2, respectively. The latter value of View the MathML sourceB0 matches very well with the mean barrier height obtained from the plot ofϕap versus q/2kT. The Richardson constant is much closer to the theoretical value of 146 A/cm2 K2.
The series resistance Rs is also estimated from the forward current–voltage characteristics of Mo/4H–SiC Schottky contact. This parameter shows strong temperature dependence. The T0 effect is validated for the 298–498 K temperature range for the used Schottky diode and provides a clear evidence for the barrier inhomogeneity at the Mo/4H–SiC interface. Finally, we note the impact of the implantation process as well as the choice of the used ion on the characterized parameters of the Schottky contact.