A ONE-SIZE-FITS-ALL UNIVERSAL SUBSTRATE for semiconductors has been created, potentially allowing researchers to deposit crystals of many previously incompatible materials onto a semiconductor surface. If the unit cell of a crystal differs in dimensions by as little as 1% from the dimensions of the surface onto which it is deposited, defects can form which prevent the proper functioning of the material. Yu-Hwa Lo (607- 255-5077) and his colleagues at Cornell have created a thin gallium arsenide film whose crystal axis is rotated slightly relative to that of the gallium arsenide substrate onto which it was deposited. The resulting surface, known as a "compliant surface," became more receptive to bonding with crystals of different materials, with the interface between the substrate and the deposited crystals forming a "twist boundary." Onto the GaAs surface, the researchers successfully deposited crystals of InGaP, GaSb, and InSb. The lattice mismatches between crystal and surface were as high as 15 percent, but the density of defects was reduced by a factor of 10⁵ compared to that for regular substrates. Moreover, if gallium nitride (mismatch of 20%) could be deposited onto this surface, the researchers believe that high-quality blue and ultraviolet semiconductor lasers might result. They expect that their approach could allow computer chips of many different types to exist on the same motherboard. (Applied Physics Letters, 31 March 1997; more text and pictures in Cornell News Release)