I need help with this question. In the recitation, we connected the '+' of the DMM to the hot side (128°C) and the '-' to the room temperature side (25°C). We got V = -54 mV, and I = -17 μA. Based on the polarity of the voltage and current, how can we tell if it's n-type or p-type?
In last week's recitation, you attached contacts to a bar of silicon and measured its dimensions and resistance. From those measurements, hopefully, you calculated the resistivity of the silicon. In this week's recitation, you heated one end of the silicon and cooled the other end, and measured the thermally generated voltage. From the polarity of the thermally generated voltage, you can determine whether your silicon was n-type or p-type. Using the type and resistivity and assuming the material is not strongly compensated or odd in some other way, you can use Neamen figure 5.4a to find the doping concentration for your silicon. Using the doping concentration and the temperature differential across your bar, you can calculate the steps described above for your silicon sample, find the carrier type, and compare the voltages you calculate and measured. Sketch the band diagrams for the hot and cold ends of your silicon and find the position(s) of the Fermi level. Remember that the effective density of states varies with temperature. Sketch the band diagram for the sample with a temperature gradient for both open circuit and short circuit conditions. Also, sketch the potential diagram for the sample with positive up for both open circuit and short circuit conditions. You don't know where zero is for potential, so consider the lowest potential as zero. Also, report the members of the recitation team with whom you did the experiment. This is an example of a problem that is difficult to do precisely, but by making reasonable approximations, you can obtain useful answers. You might begin by considering the ends of the bar and then make reasonable assumptions and approximations to finish the problem.