For a semiconductor material, the conventional flat band energy diagram is shown in the figure. The variables Y, X respectively are: 
A semiconductor \( pn \) junction at thermal equilibrium has the space charge density \( \rho(x) \) profile as shown in the figure. The figure that best depicts the variation of the electric field \( E \) with \( x \) is ( \( W \) denotes the width of the depletion layer): 
For a forward biased p-n junction diode, which one of the following energy-band diagrams is correct? (\( \epsilon_F \) is the Fermi energy) 