An ideal n+/p diode has only the quasi neutral p region of length L illuminated with light such that GL electrons/cm3-s are generated uniformly throughout the region. There is no photo-generation occurring elsewhere in the diode. Derive the current vs. applied voltage VA for this diode by answering the following questions. Since the diode is n+/p, we need only determine excess carrier concentration on the p side of the device.
a)Following the ideal diode derivation, where in the diode will the current density be evaluated?
b)What is the simplified form of the minority carrier diffusion equation in the quasi-neutral p region of the diode? What is the general form of the solution?
c)What are the boundary conditions for the quasi p region of the diode assuming an external voltage VA is applied and light is illuminated on the p side? Assume L approaches an infinite value (i.e. L >> Ln ) and any injection of excess carriers is low level.
d)From the general solution and the boundary conditions, determine the expression for the I-V characteristics of this photo-diode.