Obtaining simultaneously high crystallinity and sub-bandgap absorption in femtosecond laser hyperdoped black silicon using ion beam etching

Simon Paulus,Friedemann Völklein,Stefan Kontermann,Patrick Mc Kearney

doi:10.1063/5.0044678

Abstract

Femtosecond laser sulfur hyperdoped silicon (fs-hSi) is capable of absorbing photons in the infrared spectral range while simultaneously exhibiting negligible reflection. However, laser processing creates detrimental amorphous and polycrystalline silicon surface layers impairing electronic properties, especially reducing minority charge carrier lifetimes. This paper demonstrates how to selectively remove these disadvantageous layers by ion beam etching, while crystalline IR-absorbing silicon underneath is left. The increase in silicon crystallinity is quantified by laterally probing the fs-hSi samples with Raman spectroscopy.

Highlights

Texturing of silicon can be achieved by irradiating the surface with ultrashort laser pulses1 and leads to a low reflective surface morphology
This paper introduces a different approach and restores a crystalline silicon surface by removing the laser induced amorphous and polycrystalline silicon layers with an ion beam etching (IBE) process
This work shows that IBE successfully increases the crystallinity of Femtosecond laser sulfur hyperdoped silicon (fs-hSi) while conserving the cone-like microstructures and IR absorption properties

Summary

Introduction

Texturing of silicon can be achieved by irradiating the surface with ultrashort laser pulses1 and leads to a low reflective surface morphology. Higher doping concentrations lead to lower charge carrier mobility, which impedes carrier extraction.17,19 the laser process creates amorphous and polycrystalline surface layers.4 These highly recombinative layers reduce the effective minority carrier lifetime in fs-hSi and impede charge carrier extraction in optoelectronic applications.

Results

Conclusion