EBIC Studies of Individual Defects in Lightly Doped Semiconductors: CdTe as an Example

Abstract

Electron beam induced current (EBIC) experiments performed in the scanning electron microscope (SEM) are well-known to provide unique information, at a local scale, on bulk inhomogeneities and on electrically active extended defects in semiconductors1. The EBIC current arises from the collection of minority carriers created by the incident electron beam which are drifted by the electric field of a Schottky diode or of a p-n junction; they have been created in the space charge region (SCR) of the junction or they have reached the SCR by diffusion in the bulk of the semiconductor. The EBIC current is therefore material dependent through the minority carrier diffusion length L and through the SCR width W (W decreases when the doping level increases). Only the Schottky diode configuration where the junction is parallel to the surface and perpendicular to the electron beam, will be discussed in this paper, as it allows both imaging and quantitative characterization of bulk parameters of the semiconductor, as well as of extended defects. The accelerating beam voltage E0 used in EBIC experiments is also an important parameter, as it controls the electron penetration depth R of incident electrons in the material, and thus the depth from which the electrical information comes. The minority carriers created at a depth from the surface greater than W+L do not contribute to the collected current.