Gold-Hyperdoped Germanium with Room-Temperature Sub-Band-Gap Optoelectronic Response

Short-wavelength-infrared (SWIR; 1.4-3.0 μm) photodetection is important for various applications. Inducing a low-cost silicon-compatible material, such as germanium, to detect SWIR light would be advantageous for SWIR applications compared with using conventional (III-V or II-VI) SWIR materials. Here, we present a scalable nonequilibrium method for hyperdoping germanium with gold for dopant-mediated SWIR photodetection. Using ion implantation followed by nanosecond pulsed laser melting, we obtain a single-crystal material with a peak gold concentration of 3 × 1019cm-3 (103 times the solubility limit). This hyperdoped germanium has fundamentally different optoelectronic properties from those of intrinsic and conventionally doped germanium. This material exhibits sub-band-gap absorption of light up to wavelengths of at least 3 μm, with a sub-band-gap optical absorption coefficient comparable to that of commercial SWIR photodetection materials. We show that germanium hyperdoped with gold exhibits sub-band-gap SWIR photodetection at room temperature, in contrast with previous doped-germanium photodetector studies, which only show a low-temperature response. This material is a potential pathway to low-cost room-temperature silicon-compatible SWIR photodetection.