Hyperdoped silicon materials: from basic materials properties to sub-bandgap infrared photodetectors

Abstract

Hyperdoping silicon, which introduces deep-level dopants into Si at concentrations near one atomic percent, drastically changes its optoelectronic properties. We review recent progress in the fundamental understanding of the material properties and state of the art sub-bandgap infrared photodetectors. Different hyperdoping techniques are reviewed and compared, namely ion implantation followed by pulsed laser melting (PLM) or other fast annealing methods and PLM of Si with a dopant precursor. We review data available in the literature for material properties related to the success of optoelectronic devices such as the charge carrier lifetime, mobility, and sub-bandgap light absorption of hyperdoped Si with different dopants. To maximize carrier generation and collection efficiency in a sub-bandgap photodetector, charge carrier lifetimes must be long enough to be transported through the hyperdoped layer, which should be on the order of light absorption depth. Lastly, the charge transport properties and photodetector responsivities of hyperdoped Si based photodiodes at room temperature and at cryogenic temperatures are compared. The charge carrier transport mechanisms at different temperature ranges and in different dopant systems are discussed. At room temperature, despite different dopant energetics and hyperdoped thicknesses, light detection exhibits similar spectral responsivities with a common cutoff around 0.5 eV, and at low temperatures, it extends further into the infrared range. The roles of the dopant energetics and process-induced defects are discussed. We highlight future material development directions for enhancing device performance.