To date, it has not been possible to combine optical and electrical functions on a single silicon chip because silicon light emitters were too inefficient.
The new technology is based on a structure in which ions of rare earth metals such as erbium and cerium are implanted in a layer of Silicon Rich Oxide - silicon dioxide that has been enriched with silicon nanocrystals smaller than two nanometers in diameter. The light emitters are 100 times more efficient than any previous silicon-based emitters and are comparable to traditional products, STM said. The frequency of the emitted light varies depending on the metal used, STM said.
One of the first applications for the technology has been to build power control devices with the control circuitry electronically isolated from the power switching transistors. Electrical isolation is mandatory in many applications for safety reasons and until now it has been necessary to use external devices such as relays and transformers.
Now STM has been able to develop two circuits on one chip, separated from one another by insulating silicon dioxide but communicating with one another using silicon light emitters and detectors. These will be useful in applications where the power circuit has to handle much higher voltages than the control circuit, STM said.
The company has patented the key techniques of implanting the rare earth ions. The technology is compatible with existing high-volume production processes, so will not be expensive to implement, STM said.