The cause of potential barrier in a P-N junction diode is :

Question

$\begin{array}{1 1} (1)\; \text{Concentration of positive and negative ions near the junction } \\ (2)\; \text{Concentration of positive charges near the junction} \\ (3)\; \text{Depletion of negative charges near the junction} \\ (4)\; \text{Increment in concentration of holes and electrons near the junction} \end{array}$