The electrical forming phenomena on the etched surfaces ofn‐type Ge crystals by ac voltages were studied thermoelectrically. Remarkable improvements in the i‐v characteristics were obtained by applying appropriate forming voltages. The thermoelectric current observed on the etched surface showedn‐type direction but it was converted top‐type by the forming. It has also been found out that the thermo‐emf depends sensitively on the pressure of the whisker contact after the forming (and on the polished surface), while the dependence is small before the forming on the etched surface.Experimental results seem to show that some substance of relatively high resistivity and ofp‐type thermo‐emf is produced by the forming between the whisker metal and the Ge surface.