CMOS-compatible germanium-tin on silicon could make inexpensive IR camera sensor
Researchers at the University of Arkansas (Fayetteville, AK) have fabricated a new form of semiconductor photodetecting material -- germanium tin (GeSn) deposited in layers on a substrate of silicon (Si) -- that could be used to build better and less expensive infrared cameras.
Researchers at the University of Arkansas (Fayetteville, AK) have fabricated a new form of semiconductor photodetecting material -- germanium tin (GeSn) deposited in layers on a substrate of silicon (Si) -- that could be used to build better and less expensive infrared cameras.1
The structures were grown using commercially available chemical-vapor-deposition (CVD) equipment; the process is Si CMOS-compatible.
The researchers optically and electrically characterized GeSn photoconductors having a 0.9%, 3.2%, and 7.0% Sn content at temperatures from 77 K to room temperature. The maximum long-wavelength response to a 2.1 µm wavelength occurred for the device with the 7.0% Sn content.
Room temperature OK, cryogenic better
Cooling to cryogenic temperatures boosted the DC responsivity at 1.55 µm by around a factor of 100 for all Sn proportions.
"The performance of these simple structures indicates a promising future for germanium tin photodetectors," says Fisher Yu, associate professor of electrical engineering. "The crystalline growth of these samples in a commercially available reactor allows for these infrared detectors to be available for expedient commercial implementation."
Only a few other research groups are working with GeSn to produce semiconductor material for computer chips and electronics. The material has potential for other applications, including lasers and high-efficiency solar cells.
The research group is collaborating with ASM International, a private company that builds machine-epitaxy tools for fabricating microelectronics devices. The researchers have also started Arktonics (also in Fayetteville) to investigate future commercialization of GeSn materials and devices.
1. Benjamin R. Conley et al., Optics Express (2014); http://dx.doi.org/10.1364/OE.22.015639