Depth profiling of the minority-carrier diffusion length in intrinsically gettered silicon by electron-beam-induced current

Abstract

A new electron-beam-induced current method is proposed for the depth profiling of nonuniform minority-carrier diffusion lengths in semiconductors. An induced current scan is obtained on a Schottky diode formed on the surface of a beveled sample and converted into a collection efficiency profile η(z). From this profile the depth distribution of the diffusion length L(z) is deduced using a direct reconstruction algorithm. To check consistency, a propagation-matrix based method is developed to calculate η(z) for arbitrary L(z). The model underlying these measurements, in its more general form, holds for an extended generation and includes the presence of the depletion layer. The proposed method is tried both on artificial data and experimental η(z) profiles obtained in intrinsically gettered silicon samples. The results show, in particular, that the trend of L(z) does not, in general, follow that of η(z). The connection between charge-collection efficiency and the diffusive component of the reverse current of a diode with nonuniform L(z) is also discussed.