Chalcogen-hyperdoped germanium for short-wavelength infrared photodetection

Abstract

Obtaining short-wavelength-infrared (SWIR; 1.4 μm-3.0 μm) room-temperature photodetection in a low-cost, group IV semiconductor is desirable for numerous applications. We demonstrate a non-equilibrium method for hyperdoping germanium with selenium or tellurium for dopant-mediated SWIR photodetection. By ion-implanting Se or Te into Ge wafers and restoring crystallinity with pulsed laser melting induced rapid solidification, we obtain single crystalline materials with peak Se and Te concentrations of 1020 cm-3 (104 times the solubility limits). These hyperdoped materials exhibit sub-bandgap absorption of light up to wavelengths of at least 3.0 μm, with their sub-bandgap optical absorption coefficients comparable to those of commercial SWIR photodetection materials. Although previous studies of Ge-based photodetectors have reported a sub-bandgap optoelectronic response only at low temperature, we report room-temperature sub-bandgap SWIR photodetection at wavelengths as long as 3.0 μm from rudimentary hyperdoped Ge:Se and Ge:Te photodetectors.