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 $\stackrel{}{}$_B0=1.160 eV and σ₀=88.049 mV, respectively.

However, by means of the modified Richardson plot ${}_{}{}^{\mathrm{}}{}^{\mathrm{}}{}_{\mathrm{}}^{\mathrm{}}\mathrm{}{}^{\mathrm{}}{}^{\mathrm{}}$ versus q  /kT  , the mean barrier height and the Richardson constant values obtained are $\stackrel{}{}$_B0=1.139 eV and A  ^*=129.425 A/cm² K², respectively. The latter value of $\stackrel{}{}$_B0 matches very well with the mean barrier height obtained from the plot ofϕ_ap versus q/2kT. The Richardson constant is much closer to the theoretical value of 146 A/cm² K².

The series resistance R_s 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.

Keywords

• Mo/4H–SiC Schottky diodes; 
• Metal/semiconductor interface; 
• Barrier height inhomogeniety; 
• T₀ effect;
• Aluminum ion implantation
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• SOURCE:SCIENCEDIRECT
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