List of top Electronic Devices Questions on Semiconductor

A p-type semiconductor in steady state has excess minority carriers zero at $x=\pm 2L_n$, with $L_n = 10^{-4}$ cm. Electron charge $q = -1.6\times 10^{-19}$ C. The recombination rate profile is \[ R = 10^{20} \exp\left(-\frac{|x|}{L_n}\right)\ \text{cm}^{-3}\text{s}^{-1}. \] The magnitude of electron current density at $x=+2L_n$ is __________ mA/cm$^2$ (rounded to two decimals).
Select the CORRECT statement(s) regarding semiconductor devices.
Consider a long rectangular bar of direct bandgap $p$-type semiconductor. The equilibrium hole density is $10^{17}\,\text{cm}^{-3}$ and the intrinsic carrier concentration is $10^{10}\,\text{cm}^{-3}$. Electron and hole diffusion lengths are $2\,\mu$m and $1\,\mu$m, respectively. The left side of the bar ($x=0$) is uniformly illuminated with a laser having photon energy greater than the bandgap of the semiconductor. Excess electron-hole pairs are generated ONLY at $x=0$ because of the laser. The steady state electron density at $x=0$ is $10^{14}\,\text{cm}^{-3}$ due to laser illumination. Under these conditions and ignoring electric field, the closest approximation (among the given options) of the steady state electron density at $x=2\,\mu\text{m}$ is ______________.
In a non-degenerate bulk semiconductor with electron density $n = 10^{16}$ cm$^{-3}$, the value of $(E_C - E_{Fn}) = 200$ meV, where $E_C$ and $E_{Fn}$ denote the conduction band edge and electron Fermi level, respectively. Assume thermal voltage as 26 meV and intrinsic carrier concentration as $10^{10}$ cm$^{-3}$. For $n = 0.5 \times 10^{16}$ cm$^{-3}$, the closest approximation of $(E_C - E_{Fn})$, among the given options, is ________________.