A SEM-EBIC minority-carrier diffusion-length measurement technique

A SEM-EBIC minority-carrier diffusion-length measurement technique is described, whereby an arrangement is used such that the electron beam is incident normal to the charge-collecting barrier; the barrier may be either that of a Schottky diode or of a shallow p-n junction. The beam is slowly moved away from the barrier and the diffusion length is found by analyzing the resulting EBIC decay. It is shown that in many practical cases this decay is given by
I(d) \propto \exp (-d/L)/d^{3/2}
where
L
is the diffusion length and d the beam-to-diode distance. Some experimental details concerning the application of the technique are discussed, and finally the technique is used to measure the diffusion length of a number of Si and GaP samples.