History in the making
4 Sep 2001
Motorola scientists are claiming to be the first to successfully combine the best properties of silicon with the speed and optical capabilities of III-V compound semiconductors.
The discovery opens the door to significantly less expensive optical communications, high-frequency radio devices and high-speed microprocessor-based subsystems.
'This is a tremendous achievement by our scientists and one that has the potential, when fully commercialised, to transform the industry in a way that is similar to the transition from discrete semiconductors to integrated circuits,' said Dennis Roberson, senior vice president and chief technology officer of Motorola.
The technology itself enables very thin layers of III-V semiconductor materials (which include gallium arsenide, indium phosphide, gallium nitride and other high performance / light-emitting compounds) to be grown on a silicon substrate. Until now, this has been a virtually impossible task due to fundamental material mis-match issues.
Specifically, the underlying crystalline structures of silicon and the various III-V compounds do not match. As a result, previous industry attempts to combine them resulted in dislocations or 'cracks' in the material as the two mismatched structures struggled to bond.
The key to solving the problem was introducing an intermediate layer of material between the silicon and the III-V material. The solution was found in discovering exactly the right 'recipe' for a material that would easily bond with both silicon and GaAs, reducing the strain between the two target materials in the process.
The idea was originally developed by Motorola Labs' scientist, Dr. Jamal Ramdani. Developing and proving the exact recipe and process grew out of work done by a broad team of scientists and engineers. Motorola Labs is now working on developing the optimum intermediate layer for indium phosphide and other materials.
Motorola Labs created the world's first 8' GaAs on silicon wafer and worked with epitaxial wafer manufacturer IQE to create the world's first 12-inch GaAs on silicon wafers and a variety of other wafer sizes.
Motorola then made working power amplifiers from GaAs on silicon wafers and successfully completed numerous wireless calls using those devices in several phones over the past few months. In addition, a light-emitting device was created to demonstrate the optical characteristics.
'GaAs on silicon is just the first step and has created a baseline technology for extending our research to other materials systems,' said Dr. Jim Prendergast, vice president and director, Motorola Labs, Physical Sciences Research Lab. 'One of our next goals is to complete the task of growing indium phosphide on silicon. This technology should support chip clock speeds of more than 70GHz and long-wavelength lasers that are critical to fibre-optic communications.'
Motorola has filed more than 270 patents on inventions related to this new technology and the company intends to broadly license the technology. Padmasree Warrior, a Motorola corporate vice president has been selected to lead the commercialisation effort.
'Motorola's announcement that they have successfully made GaAs transistors in a thin layer of GaAs grown on a silicon wafer could go down in history as a major turning point for the semiconductor industry,' said Steve Cullen, director & principal analyst, Semiconductor Research, Cahners In-Stat Group.
