Diode Currents 

Similarly we obtain at the p side

as shown in Fig 10.6

Abrupt junction with P + doping voltage drop in p + is neglected

V = Constant for one sided abrupt junctions.

For Ge ideal equation is valid.

For GaAs and Si only qualitative agreement as shown in Fig 10.7

This variation is due to:-

.  surface effects.

.  generation and recombination.

.  tunneling of carriers between states in the bandgap.

.  High injection conditions.

.  Series resistance effect.

Under Reverse Bias the generation current, for a generation rate of G per unit volume is

Therefore, one sided diode (N A >>N D ) the reverse bias current

J R is dominated by the diffusion and Shockley equation is followed.

For Si and GaAs, may be small and the generation term may be comparable or dominant.

Under Forward bias the major R-G process in the depletion region is a capture process.

The Recombination current density is given by

where is the effective recombination lifetime.