For the given circuit of a $PN-$ junction diode,which of the following statements is correct?

Which of the following is correct with respect to the following statements? Due to diffusion of electrons from $n$ to $p$-side:
$I$. electrons are accumulated in the depletion region.
$II$. electron drift current is from $p$-side to $n$-side.
$III$. an ionised donor is left in the $n$-region.
$IV$. electrons of $n$-side come to $p$-side and electron-hole combination takes place in $p$-side.
Select the correct option from the following.

$A$ $P-N$ junction is formed using $Si$ material. What is the approximate height of the depletion barrier in $V$?

Which is the wrong statement in the following sentences? $A$ device in which $P$ and $N$-type semiconductors are used is more useful than a vacuum tube because:

Which of the following figures represents a forward-biased diode?

The depletion layer in a silicon diode is $1 \, \mu m$ wide and the knee potential is $0.6 \, V$. The electric field in the depletion layer is: