What is a depletion barrier?

(N/A) depletion barrier,also known as a depletion region or depletion layer,is a region formed at the $P-N$ junction where mobile charge carriers (electrons and holes) have diffused across the junction and recombined.
$1$. Due to this recombination,the region near the junction becomes depleted of mobile charge carriers.
$2$. On the $P$-side,the region contains negatively charged immobile acceptor ions,and on the $N$-side,it contains positively charged immobile donor ions.
$3$. This creates an electric field directed from the $N$-side to the $P$-side,which opposes further diffusion of charge carriers.
$4$. The potential difference across this region is called the barrier potential or depletion barrier,which acts as an obstacle to the flow of current across the junction.