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

Abstract

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 dopantmediated SWIR photodetection. Using ion implantation followed by nanosecond pulsed laser melting, we obtain a single-crystal material with a peak gold concentration of 3 × 10 19 cm −3 (10 3 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.

A highly ordered and damage-free Ge inverted pyramid array structure for broadband antireflection in the mid-infrared

“…Novel Ge-based mid-infrared (MIR) photodetectors based on sub-band absorption have also been explored by means of constructing heterostructures 7,8 and hyperdoping. 9,10 In addition, Ge-based waveguide photonics in MIR range have been researched extensively. 1,2 It is worth noticing that a good interface quality (i.e., single crystallinity with the minimized amount of surface defects) is highly required for the heterostructure-based optoelectronic devices.…”

Heavily Doped Zinc Oxide with Plasma Frequencies in the Telecommunication Wavelength Range

“…To date, there are only a few reports about hyper-doped materials, because nonequilibrium preparation processes are required to overcome the SSL. [15][16][17][18][19][20] Hyper-doped silicon was realized by femtosecond laser irradiation in a sulfur and nitrogen atmosphere, which resulted in very rough surfaces with microstructures. [15] Another procedure for hyper-doping is the use of ion implantation and a subsequent short-time annealing process.…”

Flexible Titanium Nitride/Germanium-Tin Photodetectors Based on Sub-Bandgap Absorption

“…In addition, the integration of a high-Sn alloy with Ge is a promising approach for high peak responsivity and detectivity in short-wavelength infrared (SWIR) even to mid-infrared (MIR) due to the efficient transition from an indirect to a direct bandgap. , Another practical method is sub-bandgap absorption in which the metallic layer absorbs the photons to generate hot carriers, followed by injection of the hot carriers into GeSn by going over the SBH between the GeSn and metal, which is usually smaller than the bandgap of GeSn. Dopant-mediated sub-bandgap Ge PDs with supersaturated concentrations of gold (Au) have been reported, which are able to extend photoresponse to the SWIR region . Therefore, it is worth exploring further how to couple sub-bandgap absorption into GeSn.…”

“…Dopant-mediated sub-bandgap Ge PDs with supersaturated concentrations of gold (Au) have been reported, which are able to extend photoresponse to the SWIR region. 18 Therefore, it is worth exploring further how to couple sub-bandgap absorption into GeSn.…”