GATE Electronics and Communications (EC) 2021 Solved Paper

The energy band diagram of a p-type semiconductor bar of length L under equilibrium condition (i.e., the Fermi energy level E_F is constant) is shown in the figure. The valance band E_V is sloped since doping is non-uniform along the bar. The difference between the energy levels of the valence band at the two edges of the bar is Δ.
 
If the charge of an electron is q, then the magnitude of the electric field developed inside this semiconductor bar is