Semiconductor Laboratory
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Semiconductor Laboratory | |
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Schottky diodesA Schottky contact is a contact between a metal and a semiconductor. The current voltage characteristics are, $$I = I_S\left(\exp\left(\frac{eV}{k_B T}\right) - 1\right)\hspace{0.5cm}\text{[A]}$$In forward bias where the exponential term is much larger than the -1 term, you can take the logarithm to get, $$\ln(I) = \ln(I_S)+\frac{eV}{k_B T}$$so if you plot $\ln(I)$ vs. $V$ you should get a straight line with a slope of $\frac{eV}{k_B T}$ and the intercept will be $\ln(I_S)$. This way you can determine $I_S$ for different temperatures. For thermionic emission, the saturation current should have the form, $$I_S = \frac{Aem^*k_B^2}{2\pi^2\hbar^3}T^2\exp\left(-\frac{\phi_b}{k_BT}\right)$$Here $A$ is the area of diode, $m^*$ is the effective mass of the charge carrier, $\phi_B$ is the Schottky barrier, and $T$ is the absolute temperature. $$\ln\left(\frac{I_S}{T^2}\right) = \ln\left( \frac{Aem^*k_B^2}{2\pi^2\hbar^3}\right) -\frac{\phi_b}{k_BT}$$If you plot $\ln\left(\frac{I_S}{T^2}\right)$ vs. $1/T$ the slope of the line will give the Schottky barrier. |