GENEVA, Switzerland -- STMicrolectronics claims to have achieved a breakthrough in the creation of light-emitting silicon and said it would have engineering samples of monolithic silicon devices based on the technology, combining electrical isolation and optical communication, before the end of 2002.
The development allows silicon light emitters to match the efficiency of compound semiconductor materials such as gallium arsenide for the first time, the company said.
The company did not quantify the wavelength of light that had been obtained from silicon or the efficiency of the electrical-to-optical conversion achieved. It did say the quantum efficiency was 100 time higher than that previously achieved.
The company did say that the development could allow a number of applications in which optical and electrical functions are combined on a single silicon chip. This was not previously practical because although silicon is the favored material for complex microelectronic circuits, it is difficult to form into an efficient light emitter.
"The ability to combine optical and electronic processing on the same chip presents enormous opportunities for ST to be the first to develop many new types of semiconductor products, especially as the technology is compatible with existing volume production process flows and equipment. ST has already identified a number of promising applications and key manufacturing issues have already been solved so that the technology can be rapidly moved into production," said GianGuido Rizzotto, director, corporate technology R&D, STMicroelectronics, in a statement.
ST's light emitting silicon is based on the implanting of ions of rare-earth metals such as erbium or cerium, in a layer of silicon rich oxide (SRO), such as silicon dioxide enriched with silicon nanocrystals of one or two nanometers diameter.
"The quantum efficiencies achieved are about 100 times better than has previously been possible with silicon and are, for the first time, comparable to those obtained from gallium arsenide and other compound semiconductors traditionally used to make light-emitting diodes," said Salvo Coffa, manager of the team responsible for the development, in a statement.
Similar breakthroughs have been claimed in the past but proved difficult to commericalize. One such was the development of visible-light emitting porous silicon in the early 1990s. The isotropic etching of silicon was used to produce a coral-like structure with nanometer-dimensioned filaments.
In ST's technology the frequency of the emitted light depends on the choice of rare-earth dopant and the company said it has patented techniques for implanting the rare-earth ions into the silicon.
One of the first applications of the new technology is to build power control devices in which the control circuitry is electrically isolated from the power switching transistors. Such opto-isolation is done at present with separate devices.
ST has patented a structure in which two circuits, built on the same chip are electrically separated from each other by insulating silicon dioxide, but communicate via optical signals using integrated silicon light emitters and detectors. Engineering samples will be available by the end of 2002, the company said.
