AmberWave Systems Corporation, Salem, NH, has devised a way to combine silicon (Si) with high-speed, opto-electronic semiconducting materials like germanium (Ge) and gallium arsenide (GaAs) on a single wafer.
According to AmberWave, the new technique will significantly reduce the cost of opto-electronic devices ranging from space solar cells to communications lasers. Perhaps more importantly, the technology may soon enable new integrated devices such as high-performance opto-electronics with Si microelectronics on a single chip.
Typically, silicon and compound semiconductor materials cannot be combined because of their different crystal structures. This disparity creates stress between the materials and ultimately causes devices to fail.
AmberWave gets around that by building a buffer layer on the Si substrate. Layers are deposited from 100-percent Si to 100-percent Ge with a SiGe interlayer. Patented chemical-mechanical polishing techniques are used to eliminate surface crosshatch roughness and minimise any line defects that could create preformance problems for devices created on top of the SiGe interlayer.
The potential of AmberWave’s SiGe interlayer technology is said to have been successfully demonstrated by creating detector-type devices, including single- and dual-junction AlGaAs/GaAs and InGaP/GaAs photovoltaic cells.
The goal for these devices is comparable performance to solar cells made with III-V compounds on Ge substrates but with lighter weight, lower cost, and improved robustness.
The company estimates the weight decrease for replacing a Ge substrate with silicon to be 65 percent, which would more than double the power output per unit of weight. In addition, Si substrates can be produced in larger diameters than Ge substrates, which leads to a 50-percent cost reduction in manufacturing.
A more difficult task is creating emitter-type devices, such as communications lasers, that integrate the functions of compound materials and silicon on a single chip.
AmberWave is currently building a 980-nanometer laser that will eventually be integrated with Si microelectronics for on-chip and chip-to-chip input/output functions. A prototype developed at MIT based on technology licensed by AmberWave already shows life spans of several hours.
Currently, AmberWave is looking for development and commercialisation partners from the solar cell and high-speed communications industries.