On the Optoelectronic Mechanisms Ruling Ti-hyperdoped Si Photodiodes

This work deepens the understanding of the optoelectronic mechanisms ruling hyperdoped-based photodevices and shows the potential of Ti hyperdoped-Si as a fully complementary metal-oxide semiconductor compatible material for room-temperature infrared photodetection technologies. By the combination of ion implantation and laser-based methods, approximate to 20 nm thin hyperdoped single-crystal Si layers with a Ti concentration as high as 10(20) cm(-3) are obtained. The Ti hyperdoped Si/p-Si photodiode shows a room temperature rectification factor at +/- 1 V of 509. Analysis of the temperature-dependent current-voltage characteristics shows that the transport is dominated by two mechanisms: a tunnel mechanism at low bias and a recombination process in the space charge region at high bias. A room-temperature sub-bandgap external quantum efficiency (EQE) extending to 2.5 mu m wavelength is obtained. Temperature-dependent spectral photoresponse behavior reveals an increase of the EQE as the temperature decreases, showing a low-energy photoresponse edge at 0.45 eV and a high-energy photoresponse edge at 0.67 eV. Temperature behavior of the open-circuit voltage correlates with the high-energy photoresponse edge. A model is proposed to relate the optoelectronic mechanisms to sub-bandgap optical transitions involving an impurity band. This model is supported by numerical semiconductor device simulations using the SCAPS software.