Fabricating Ohmic contacts to Au hyperdoped Si for infrared photodetector applications

Abstract Recently, hyperdoped Si has gained interest as an infrared material for photodetectors due to the possible formation of intermediate bands inside the Si band gap. In particular, Au-hyperdoped Si has been demonstrated to exhibit a sub-band gap photoresponse, but efficiencies remain low. To achieve high efficiency Au-hyperdoped Si (Si:Au) photo devices, we develop a recipe for Ohmic contact to Si:Au materials by understanding the properties of the interfacial region. In this work, we show that Si:Au can form an Ohmic contact, which is relatively independent of the contacting metal due to Fermi pinning behavior. Degenerate boron doping decreases the contact resistivity by 1 order of magnitude, because the Si:Au resistivity decreases immediately below the contact. Cr/Ni/Au 5/200/200 nm metal stacks with boron doping exhibit the lowest specific contact resistivity (0.16 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi mathvariant="normal">Ω</mml:mi> <mml:mo>⋅</mml:mo> <mml:msup> <mml:mtext>cm</mml:mtext> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:math> ) in this work, better than Au-based contacts. We also demonstrate that the Cr silicide formation temperature causes the relocation of Au atoms and degrades sub-band gap behavior.