Selenium segregation in femtosecond-laser hyperdoped silicon revealed by electron tomography

Abstract:

Doping of silicon with chalcogens (S, Se, Te) by femtosecond laser irradiation leads to nearunity optical absorptance in the visible and infrared range and is a promising route towards siliconbased infrared optoelectronics. However, open questions remain about the nature of the infrared absorptance and in particular about the impact of the dopant distribution and possible role of dopant diffusion. Here we use electron tomography using a high-angle annular dark field (HAADF) detector in a scanning transmission electron microscope (STEM) to extract information about the threedimensional distribution of selenium dopants in silicon and correlate these findings with the optical properties of selenium- doped silicon. We quantify the tomography results to extract information about the size distribution and density of selenium precipitates. Our results show correlation between nanoscale distribution of dopants and the observed sub- band gap optical absorptance, and demonstrate the feasibility of HAADF-STEM tomography for the investigation of dopant distribution in highly-doped semiconductors.