The same MOSFET can be worked in enhancement mode, if we can change the polarities of the voltage VGG. So, let us consider the MOSFET with gate source voltage VGG being positive as shown in the following figure.
When no voltage is applied between gate and source, some current flows due to the voltage between drain and source. Let some positive voltage is applied at VGG. Then the minority carriers i.e. holes, get repelled and the majority carriers i.e. electrons gets attracted towards the SiO2 layer.
With some amount of positive potential at VGG a certain amount of drain current ID flows through source to drain. When this positive potential is further increased, the current ID increases due to the flow of electrons from source and these are pushed further due to the voltage applied at VGG. Hence the more positive the applied VGG, the more the value of drain current ID will be. The current flow gets enhanced due to the increase in electron flow better than in depletion mode. Hence this mode is termed as Enhanced Mode MOSFET.
