Test: Carrier Lifetime - Electrical Engineering (EE) MCQ

Carrier lifetime is defined as the existence of any carrier for τ seconds. Carrier lifetime ranges from nanoseconds to hundreds of microseconds.

This is the first process of Schokley-Read-Hall theory of Recombination.

The recombination rate, R=δn/τ.
So, R=10¹⁴ / 10^-6
R=10²⁰.

R_cn=C_n*N_t*(1-f_F (Et))*n
Substituting the values,
R_cn=6*10³⁰.

R_en=E_n*N_t*(f_F (Et))
Substituting the values,
R_en=1.5*10¹⁰.

At thermal equilibrium, the electron capture rate and the emission rate will be same in the conduction band.

τ_p=1/(C_p*N_t )
=1/(5*10¹⁰)
=2*10^-11.

With the increase in the number of the majority carriers, the carriers for the recombination will be decreasing with the excess minority carriers and will finally become intrinsic as the concentrations will be same.

Gold is used as a recombination agent because of its chemical properties as it was used in the Bohr’s experiment. Thus the device designer can obtain the desired carrier lifetimes by introducing gold into silicon under controlled conditions.

The rate of change of the excess density depends on the density of the semiconductor and the rate with respect to time is also dependent on it.