Question

(x) [2 Marks] For the current components in a p - n junction diode at thermal equilibrium (a) Electron diffusion current equals hole diffusion current; (b) All current components are equal to zero; (c) Electron diffusion current equals electron drift current; (d) The drift current components are equal to zero; (e) All of the above; (f) None of the above;

Answer 1

Initially poles in P-side and electrons in n-side are huge in concentration holes from P-side will move into N type semiconductor. Electrons from N-side will move from into P-type semiconductor. At the junction holes and electrons will recombine leaving immobile charges. current developed in diffusion process is called diffusion current. when two opposite charges separated by some distance electric field will be formed. Due to this electric field minority carriers in n type semiconductor (holes) & in P type semiconductor (electrons) will be drifted. this current developed is called drift current. J_diffusion = J_diff (holes) + J_diff (electrons) J_drift = J_drift (holes) + J_drift (electrons) \r\n After some time J_diffusion and J_drift will become equal in magnitude & opposite in direction. J_drift oppose diffusion of carriers... equilibrium established. At equilibrium diffusion and drift currents are equal. option (c) is correct. At thermal equilibrium electron diffusion current equals electron drift current