Correlation between Resistivity and dopant concentration essays

Correlation between Resistivity and dopant concentration essays From observation alone, we can notice that the higher the concentration, the lower the resistivity. This is consistent with the Drude model, which states that the higher the concentration of conducting charges is, the higher conductivity would result. In this case, where the dopant is boron which has only three electrons in its outmost shell, the conducting would be predominantly holes, while electron conduction could only account for small part of conductivity. So theoretically, we can just consider the contribution of holes. However, we would expect some deviation due to this approximation. Among all the samples, the ones with lower dopant concentration would be expected to have more contribution from electrons, which means the resistivity would be lower than the theoretical result. Moreover, according to formula for calculation of resistivity , the tips of probes would have large resistivity, which in return depends on the extend to which the probe contact with the wafer. For different wafer, errors exist. In this sense, we would not expect the logarithm graph of the experiment to be perfect linear. Impurities and the scratches on the surface may also contribute to the errors. As we stated before, the higher the concentration, the lower the resistivity. For high concentration samples, the resistivity would be small so that the small change in current does not result in much change in voltage determined, according to the formula V=IR. We would expect the voltage readings to be quite stable. In contrast, for lower concentration samples, resistivity would be larger, and the voltage would be easily affected. So we would expect it fluctuate from time to time, as we observed in the experiment. Furthermore, because the lab has a lot of electronic appliances, such as handphones and computers, which would exert an electromagnetic field to their ambience (in fact the apparatus is just beside a computer), the Hall effect would occur ...