At room temperature,a $p$-type semiconductor has

In an $N$-type semiconductor,where are the donor energy levels $E_D$ located?

If the ratio of the number density of electrons to the number density of holes in a semiconductor is $7/5$ and the ratio of their currents is $7/4$,what is the ratio of their drift velocities?

$A$ transistor is a/an

In the energy band diagram of a material shown below,the open circles and filled circles denote holes and electrons respectively. The material is

$A$ 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 $0.53 \mathring{A}$).