STEM EBIC as a Quantitative Probe of Semiconductor Devices

TL;DR

This paper demonstrates that STEM-EBIC imaging can quantitatively analyze carrier transport in nanoscale silicon devices, revealing effects of surface recombination and FIB modifications, and highlighting its potential for detailed semiconductor characterization.

Contribution

It introduces a systematic application of STEM-EBIC to thin TEM lamellae, providing direct visualization and measurement of carrier transport properties at the nanoscale.

Findings

Effective diffusion lengths are much smaller than bulk values due to surface effects.

FIB milling induces surface modifications affecting carrier transport.

Current-voltage behavior deviates from ideal diode characteristics.

Abstract

Electron beam-induced current (EBIC) imaging in the scanning transmission electron microscope (STEM), STEM-EBIC, provides direct access to carrier transport at the nanoscale. While well established in bulk SEM geometries, its application to thin TEM lamellae remains largely unexplored. Here, we present a systematic STEM-EBIC study of silicon photodiode lamellae prepared by gallium and xenon focused ion beam (FIB) milling. We directly visualize the p-n junctions in thin cross sections and extract effective diffusion lengths for electrons and holes as a function of local thickness. The values are orders of magnitude smaller than those obtained by SEM-EBIC on bulk silicon, reflecting pronounced surface recombination and FIB-induced surface modifications. Current-voltage measurements further reveal severe deviations from the expected diode-like behavior, which we attribute to ohmic metal-semiconductor contacts in the emasurement setup. Our analysis establishes STEM-EBIC as a quantitative probe of carrier transport in nanoscale devices.