Question

Modern Physics: Solid State and Nuclear Physics

You want to use the Hall Effect to determine if a particular sample of a semiconductor is n or p doped.

a. Sketch the following configuration: the sample is placed flat on the page. The applied voltage source is attached such that the positive lead is nearest to the top of the page, and the negative near the bottom. The magnetic field goes into the page. Identify on your drawing the direction of the current through the sample, assuming the usual convention of the current which is the movement of positive charges.

b. When you hook up a voltmeter to the sample with the negative lead on the left side, and positive on the right side, you find that a positive voltage is measured. Based on this, determine the sign of your charge carriers.

c. Is the sample n-doped or p-doped? If the sample is silicon, suggest a possible identity of the doping species.

Answer 1

a)

b)

If we measure positive Hall voltage when negative lead is placed on the left side and positive on the right, that means, all the positive charges are going to the right and negative charges to the left. If the charge carriers are positive, then only we measure positive Hall voltage here. So, the charge carriers are positive.

c)

Since it contains positive holes, the material is p-doped only.

If the sample is Silicon, that is, p-type, the Hall voltage is positive. In the case of a p-type semiconductor such as Silicon, the dopent will be borron or gallium. These type of dopents will have three electrons in their outer shell. they are generally group III elements.