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

Abstract

In the present work we investigate the forward current–voltage (I–V) characteristics, over a wide temperature range 298–498K, 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 ϕB 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 ϕap versus q/2kT. The mean barrier height and the standard deviation obtained values are ϕ¯B0=1.160eV and σ0=88.049mV, respectively.However, by means of the modified Richardson plot Ln(Is/T2)−(q2σ02/2k2T2) versus q/kT, the mean barrier height and the Richardson constant values obtained are ϕ¯B0=1.139eV and A*=129.425A/cm2K2, respectively. The latter value of ϕ¯B0 matches very well with the mean barrier height obtained from the plot of ϕap versus q/2kT. The Richardson constant is much closer to the theoretical value of 146A/cm2K2.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 298–498K 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.