The number of silicon atoms per $m^3$ is $5 \times 10^{28}$. This is doped with $4.5 \times 10^{21}$ atoms $/ m^3$ of Arsenic. The ratio of the number of electrons to the number of holes after doping is (Take $n_i = 1.5 \times 10^{16} / m^3$)

Silicon is a semiconductor. If a small amount of $As$ is added to it,then its electrical conductivity . . . . . . .

$A$ donor atom in a semiconductor has a loosely bound electron. The orbit of this electron is considerably affected by the semiconductor material but behaves in many ways like an electron orbiting a hydrogen nucleus. Given that the electron has an effective mass of $0.07 \, m_e$,where $m_e$ is the mass of the free electron,and the space in which it moves has a permittivity of $13 \, \varepsilon_0$,then the radius of the electron's lowermost energy orbit will be close to ................. $\mathring{A}$ (take the Bohr radius of the hydrogen atom as $0.53 \mathring{A}$).

In $p-$type semiconductor,the majority charge carriers are

Which one of the following statements is true? $A$ p-type semiconductor is doped with

Explain the recombination coefficient of an intrinsic semiconductor and derive the relation $n_i^2 = n_e n_h$.