A tiny electrically pumped laser
DOI: 10.1063/1.4797331
A tiny electrically pumped laser has been created by bonding a wafer of III–V compounds on a silicon substrate. Because the minimum of silicon’s conduction band doesn’t line up with the maximum of its valence band, holes and electrons can’t recombine efficiently to make photons. As a result, silicon is a poor photonic material. But if its photonic shortcomings could be circumvented, silicon-based computers could tap directly into the torrents of data that flow through fiber-optic cables. To reach that goal, a silicon laser is essential. Ideally, the laser should work at room temperature, be electrically pumped, and be manufactured using lithography, epitaxy, and other techniques from the industrial repertoire. Mario Paniccia and his collaborators at Intel Corp’s research labs in Santa Clara, California, have now built a prototype that meets those requirements. Working with John Bowers of the University of California, Santa Barbara, the Intel researchers have assembled an optically active AlGaInAs heterostructure on top of an etched silicon waveguide. Ordinarily, bonding III–V compounds to silicon creates performance-sapping defects. To avoid that outcome, Bowers devised a novel low-temperature (300°C) wafer-bonding technique. At 13%, the prototype’s efficiency is modest, but Paniccia foresees improvements. As the figure shows, the researchers can already make more than 30 lasers on a single 8-mm-wide chip. (
