For a $p-$type semiconductor,which of the following statements is true?

Out of the following impurities,which impurity is not a trivalent?

Let $n_e$ be the number density of electrons and $v_d$ be the drift velocity in a semiconductor. When the temperature is increased:

$A$ potential difference of $2.5 \,V$ is applied across the faces of a germanium crystal plate. The face area of the crystal is $1 \,cm^2$ and its thickness is $1.0 \,mm$. The free electron concentration in germanium is $2 \times 10^{19} \,m^{-3}$ and the electron and hole mobilities are $0.33 \,m^2/V \cdot s$ and $0.17 \,m^2/V \cdot s$ respectively. The current across the plate will be .......... $A$.

$P$-type semiconductors are made by adding which impurity element?

In an $N$-type $Ge$ semiconductor,the mobility of electrons is $5000 \ cm^2/V \cdot s$ and the conductivity is $5 \ mho/cm$. If the effect of holes is negligible,what is the concentration of impurity atoms?