Hot-point probe

A hot point probe is a method of determining quickly whether a semiconductor sample is n-type or p-type. A voltmeter or ammeter is attached to the sample, and a heat source, such as a soldering iron, is placed on one of the leads. The heat source will cause charge carriers (electrons in an n-type, electron holes in a p-type) to move away from the lead. The heat from the probe creates an increased number of higher energy carriers which then diffuse away from the contact point. This will cause a current/voltage difference. For example, if the heat source is placed on the positive lead of a voltmeter attached to an n-type semiconductor, a positive voltage reading will result as the area around the heat source/positive lead becomes positively charged.[1] A simple explanation for experiment is that the thermally excited majority free charged carriers are translated with in the semiconductor form the hot probe to be he cold probe. The mechanism for this motion with in semiconductor is of a diffusion type since the material is uniformly doped.[2]