The four-point probe method is a common technique for measuring the resistivity and sheet resistance of semiconductor materials. Its basic principle involves placing four equally spaced probes on the sample surface. A constant current is applied through the two outer probes, and the voltage drop is measured across the two inner probes, from which parameters including resistivity and sheet resistance can be calculated.

The core advantage of the four-point probe method lies in the physical separation of the current loop and the voltage loop. Given the extremely high internal resistance of the voltmeter, virtually no current flows through the voltage measurement loop. This effectively eliminates interference from contact resistance between probes and the sample as well as wire resistance, delivering high measurement accuracy.