Scanning ultrafast electron microscopy reveals photovoltage dynamics at a deeply buried p-Si/SiO2 interface

The understanding and control of charge carrier interactions with defects at buried insulator/semiconductor interfaces is essential for achieving optimum performance in modern electronics. Here, we report on the use of scanning ultrafast electron microscopy (SUEM) to remotely probe the dynamics of excited carriers at a Si surface buried below a thick thermal oxide. Our measurements illustrate a previously unidentified SUEM contrast mechanism, whereby optical modulation of the space-charge field in the semiconductor modulates the electric field in the thick oxide, thus affecting its secondary electron yield. By analyzing the SUEM contrast as a function of time and laser fluence we demonstrate the diffusion mediated capture of excited carriers by interfacial traps.

Automated summary

Understanding and controlling the interaction of charge carriers with defects at buried insulator/semiconductor interfaces is crucial for optimal performance in electronics. This study used scanning ultrafast electron microscopy (SUEM) to investigate the dynamics of excited carriers at a Si surface buried under a thick oxide layer, revealing a previously unidentified contrast mechanism. Analysis of the contrast as a function of time and laser fluence demonstrated diffusion-mediated capture of excited carriers by interfacial traps.