Since we assume that there is no electric field in the quasi-neutral region, the current
density equations of carriers reduce to only diffusion terms and are not coupled by the
electric field. The current is based on the diffusive flows of carriers in the quasi-neutral
regions and is determined by the diffusion of the minority carriers. The minority-carrier
concentration can be calculated separately for both quasi-neutral regions. The electron
current density in the quasi-neutral region of the p-type semiconductor and the hole
current density in the quasi-neutral region of the n-type semiconductor are described by
The continuity equations (4.34) for electrons and holes in steady-state (∂n/∂t = 0 and ∂p/∂t
= 0) can be written as
Under low level injection conditions, a change in the concentration of the majority carriers
due to generation and recombination can be neglected. However, the
recombinationgeneration rate of minority carriers depends strongly on the injection and is
proportional to the excess of minority carriers at the edges of the depletion region. The
recombinationgeneration rate of electrons, R n , in the p-type semiconductor, and holes, R p ,
in the n-type semiconductor, is described by Eqs. (7.18) and (7.23),
where Δn is the excess concentration of electrons in the p-type semiconductor with respect
to the equilibrium concentration n p0 , and τ n is the electron’s (minority-carrier) lifetime. Δp
is the excess concentration of holes in the n-type semiconductor with respect to the
equilibrium concentration p n0 and τ p is the hole’s (minority-carrier) lifetime. Δn and Δp are
given by
density equations of carriers reduce to only diffusion terms and are not coupled by the
electric field. The current is based on the diffusive flows of carriers in the quasi-neutral
regions and is determined by the diffusion of the minority carriers. The minority-carrier
concentration can be calculated separately for both quasi-neutral regions. The electron
current density in the quasi-neutral region of the p-type semiconductor and the hole
current density in the quasi-neutral region of the n-type semiconductor are described by
The continuity equations (4.34) for electrons and holes in steady-state (∂n/∂t = 0 and ∂p/∂t
= 0) can be written as
Under low level injection conditions, a change in the concentration of the majority carriers
due to generation and recombination can be neglected. However, the
recombinationgeneration rate of minority carriers depends strongly on the injection and is
proportional to the excess of minority carriers at the edges of the depletion region. The
recombinationgeneration rate of electrons, R n , in the p-type semiconductor, and holes, R p ,
in the n-type semiconductor, is described by Eqs. (7.18) and (7.23),
where Δn is the excess concentration of electrons in the p-type semiconductor with respect
to the equilibrium concentration n p0 , and τ n is the electron’s (minority-carrier) lifetime. Δp
is the excess concentration of holes in the n-type semiconductor with respect to the
equilibrium concentration p n0 and τ p is the hole’s (minority-carrier) lifetime. Δn and Δp are
given by