Question

Charge density as a function of position is constant across a p-n junction, true or false

Answer 1

answer : true,

explanation : charge density as a function of position is given by, $\rho=(p-n+N^+_d-N^-_a)\cong q(N^+_d-N^-_a)$

for $-x_p$ < x < $x_n$

where it is assumed that no free carriers are present within the depletion region. For an abrupt p-n diode with doping densities, Na and Nd, the charge density is then given by:

$\rho(x)=0\\\\\rho(x)=-qN_a\\\\\rho(x)=qN_d\\\\\rho(x)=0$

see graph, here it is clear that, Charge density as a function of position is constant across a p-n junction.