The field emission current densities j from n-type semiconductors are obtained using a-fully exact calculation. scheme and are plotted in the Fowler-Nordheim (FN) coordinates. It is found that the FN plot for a semiconductor has the nonlinear slope that originates in the emission mechanism. The. slope of the FN plot has three values, each value representing the slope in the three distinct regions of field F. This implies that the tunneling probability makes three distinct contributions to the electron emission according to the value of F. It is also found that the slope is modified with the carrier concentration and the band gap. (C) 2003 American Vacuum Society.