Mid Term Review

Hyperdoping Si with deep level impurities for infrared optoelectronics

Ms Shao Qi Lim

Si hyperdoped with deep level impurities has been gaining widespread interest as a potential CMOS-compatible near- to mid-infrared sensitive photodetector operating at room temperature. Hyperdoping is achieved when the impurity concentration in Si exceeds the equilibrium solid solubility (~1016 cm-3 at 1000C) by several orders of magnitude (>1019 cm-3) such that mid-gap states introduced by the impurities form an intermediate band in the Si bandgap. In this work, Au-hyperdoped Si was fabricated by ion implantation followed by pulsed-laser melting, and the defect properties studied with Deep Level Transient Spectroscopy. Preliminary results reveal the presence of extended defects in the underlying substrate of the hyperdoped layer, affecting the substrate minority carrier lifetime in vertical-type devices. Correlating physical, optical, and electrical characterization data suggest that pn-junctions are not the ideal device structure for maximal photocarrier extraction, and current experiments on alternative device structures addressing these issues will be presented.

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