A hot point probe is a method of quickly determining whether a

semiconductor A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glas ...

sample is n-type or p-type. The sample is probed using a

voltmeter A voltmeter is an instrument used for measuring electric potential difference between two points in an electric circuit. It is connected in parallel. It usually has a high resistance so that it takes negligible current from the circuit. Ana ...

ammeter An ammeter (abbreviation of ''Ampere meter'') is an instrument used to measure the current in a circuit. Electric currents are measured in amperes (A), hence the name. For direct measurement, the ammeter is connected in series with the circuit ...

and a heat source, such as a

soldering iron A soldering iron is a hand tool used in soldering. It supplies heat to melt solder so that it can flow into the joint between two workpieces. A soldering iron is composed of a heated metal tip (the ''bit'') and an insulated handle. Heating i ...

, is placed on one of the leads. The heat will cause charge carriers (

electrons The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...

in n-type,

hole A hole is an opening in or through a particular medium, usually a solid body. Holes occur through natural and artificial processes, and may be useful for various purposes, or may represent a problem needing to be addressed in many fields of en ...

s in p-type) to move away from the lead. The heat from the probe creates an increased number of carriers, which then diffuse away from the contact point. This causes a

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...

difference. For example, if the heat source is placed on the positive lead of a

attached to an n-type semiconductor, a positive

reading will result as the area around the heat source/positive lead becomes positively charged. A simple explanation is that the thermally-excited majority free carriers move from the hot probe to the cold probe. The mechanism for this motion with in semiconductor is diffusion type since the material is uniformly doped.

References

Electronic test equipment {{Electronics-stub