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Introduction

Similar to the MOS charge and energy-band applet, but this applet allows you to learn the electric field profile and potential profile at the given applied bias to the MOS structure. The electric field and potential profiles within the semiconductor are obtained by solving the Gauss equation with the charge profile given in the second diagram.

In the depletion mode, the field and potential profile in Si is understood based on the space charge density in the depletion region. For inversion and accumulation modes, the field and protential drop in Si is contant, independent of the applied voltage. This is because all the additional charge is concentrated at the Si surface (why ? -- the induced charge increases exponentially with band-bending which is changed by the bias). This is like a 'shielding effect' by the charge at Si surface.