In Germanium,the concentration of Aluminum is $\sim 10^{21} \text{ atoms}/m^3$. The intrinsic carrier concentration in the pure semiconductor is $\sim 10^{19} /m^3$. After adding the impurity,what is the electron concentration?

$A$ $P$-type semiconductor has acceptor levels $57 \, meV$ above the valence band. The maximum wavelength of light required to create a hole is (Planck's constant $h = 6.6 \times 10^{-34} \, J-s$, speed of light $c = 3 \times 10^8 \, m/s$, charge of electron $e = 1.6 \times 10^{-19} \, C$)

What is the conductivity of a pure silicon crystal at $300 \ K$? The number of electron-hole pairs per $cm^3$ is $1.072 \times 10^{10}$. Given $\mu_n = 1350 \ cm^2/V \cdot s$ and $\mu_p = 480 \ cm^2/V \cdot s$.

Pure $Si$ at $500\, K$ has equal number of electron $(n_e)$ and hole $(n_h)$ concentrations of $1.5 \times 10^{16} \, m^{-3}$. Doping by indium increases $n_h$ to $4.5 \times 10^{22} \, m^{-3}$. The doped semiconductor is of:

The semiconductors are generally

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