The Search for Sub-Bandgap Optoelectronic Response in Silicon Hyperdoped with Gold

Deep-level dopants have been long known as the lifetime-killer in microelectronic devices. Nevertheless, it has been shown that deep-level donor can facilitate strong absorption of light with energy below the semiconductor bandgap. Due to this strong sub-bandgap absorption, it is possible to engineer silicon devices exhibiting sub-bandgap optoelectronic response, such as silicon-based infrared photodetectors and intermediate-band solar cells. In this work, we show the optoelectronic response of silicon doped with a gold concentration surpassing the equilibrium solubility limit (gold-hyperdoped silicon, Au:Si). We fabricated Au:Si by ion implantation followed by nanosecond pulse laser melting, achieving a gold dopant concentration of over 10$^{19}$ cm$^{-3}$. UV-VIS spectrophotometry was performed to measure sub-bandgap light absorption in the Au:Si layer. Our samples with the highest gold concentration have 10-15{\%} absorption of sub-bandgap light. We will present and discuss the sub-bandgap optoelectronic response of this gold-doped silicon.