The Hall effect was discovered more than 100 years ago when Hall observed a transverse voltage across a conductor subjected to a magnetic field. The technique is more powerful than the sheet resistance method because it can determine the material type, carrier concentration and carrier mobility separately.
We use the well-designed and widely-used system to measure the resistivity, carrier concentration, and mobility of the semiconductor (bulk or sheet). We can measure the Hall effects on semiconductors including Si, ZnO, SiGe, SiC, GaAs, InGaAs, InP, GaN (N-type and P-type can be measured) at room temperature and 77K.
The suitable sample size is 6mm x 6mm to 20mm x20 mm. The measurable carrier density range is 1e7 to 1e21/cm3 and the measurable mobility range is 1 to 1e7 Volt.sec. Since the Hall effect is used to measure only one layer at a time, single layer on glass should be a suitable sample for measurement. If there are two or more conducting layers connected, then the results will be some type of average of the two connected materials. | 
