Which is the primary constitutional unit for diode and transistor?

When a forward bias is applied to a $p-n$ junction,it $\qquad$ .

If in a $p-n$ junction diode,a square input signal of $10\, V$ (varying from $+5\, V$ to $-5\, V$) is applied as shown,then the output signal across $R_L$ will be:

For the circuit shown in the figure,the equivalent resistance between points $A$ and $B$ for two cases $(i)$ $V_A > V_B$ and (ii) $V_B > V_A$ is $\qquad \Omega$ and $\qquad \Omega$ respectively. ($D_1$ and $D_2$ are ideal diodes)

$A$ wafer of pure germanium crystal has two parts $X$ and $Y$. The end $X$ is obtained by doping with arsenic and $Y$ with indium. It is connected to a battery as shown in the figure. Which of the following statements is correct?

In the circuit shown in the figure,the non-zero potential difference across diode $D_{1}$ and that across diode $D_{2}$ are equal. Are the diodes identical in characteristics? Explain.