Fabrication and sub-band-gap absorption of single-crystal Si supersaturated with Se by pulsed laser mixing

Selenium supersaturated silicon layers were fab- ricated by pulsed excimer laser induced liquid-phase mixing of thin Se films on Si(001) wafers. Sufficiently low Se cov- erage avoids destabilization of rapid epitaxial solidification, resulting in supersaturated solid solutions free of extended defects, as shown by transmission electron microscopy. The amount of retained Se depends on the original film thick- ness, the laser fluence, and the number of laser pulses irradi- ating the same spot on the surface. Using this method, Se has incorporated into the topmost 300 nm of the silicon with a concentration of 0.1 at.%. Channeling Rutherford backscat- tering spectrometry measurements show that the substitu- tional fraction can be as high as 75% of the total retained Se. These alloys exhibit strong sub-band-gap absorption with optical absorption coefficient ranging up to about 10 4 cm −1 , thus making them potential candidates for applications in Si-based optoelectronic devices.