Extended Infrared Absorption in Nanostructured Si Through Se Implantation and Flash Lamp Annealing

Behrad Radfar*, Xiaolong Liu, Yonder Berencen, Mohd Saif Shaikh, Slawomir Prucnal, Ulrich Kentsch, Ville Vähänissi, Shengqiang Zhou, Hele Savin

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


Nanostructured silicon can reduce reflectanceloss in optoelectronic applications, but intrinsic silicon cannot absorbphotons with energy below its 1.1 eV bandgap. However, incorporating a highconcentration of dopants, i.e., hyperdoping, to nanostructured silicon isexpected to bring broadband absorption ranging from UV to short-wavelength IR(SWIR, <2500 nm). In this work, we prepare nanostructured silicon usingcryogenic plasma etching, which is then hyperdoped with selenium (Se) through ionimplantation. Besides sub-bandgap absorption, ion implantation forms crystaldamage, which can be recovered through flash lamp annealing. We study crystaldamage and broadband (250–2500 nm) absorption from planar and nanostructuredsurfaces. We first show that nanostructures survive ion implantationhyperdoping and flash lamp annealing under optimized conditions. Secondly, we demonstratethat nanostructured silicon has 15% higher sub-bandgap absorption (1100–2500nm) compared to non-hyperdoped nanostructure counterpart while maintaining 97% above-bandgapabsorption (250–1100 nm). Lastly, we simulate the sub-bandgap absorption ofhyperdoped Si nanostructures in a 2D model using the finite element method. Simulation results show that the sub-bandgapabsorption is mainly limited by the thickness of the hyperdoped layer ratherthan the height of nanostructures. 

Original languageEnglish
JournalPhysica Status Solidi (A) Applications and Materials Science
Early online date2 Jun 2024
Publication statusE-pub ahead of print - 2 Jun 2024
MoE publication typeA1 Journal article-refereed


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