Growth of patterned GeSn and GePb alloys by pulsed laser induced epitaxy

While modulators, waveguides and detectors have been successfully integrated in silicon devices, a laser source still remains a challenge. Unfortunately, in silicon and germanium, indirect band transitions are favored, making laser emission unlikely. Direct bandgap transitions have recently been demonstrated in germanium by introducing tensile strain with heavy n-type doping or by alloying with Sn. GePb alloys seem to be promising candidates here as well, since the required Pb concentration is predicted to be far lower than for Sn. We examine the influence of SiO
₂
hard masks on the formation of GeSn and GePb by Pulsed Laser Induced Epitaxy, a method allowing fast processing and in-situ monitoring. Main objectives are to study the spatial distribution of elements and strain as well as the possible underetching of Ge after mask removal. Sn or Pb was deposited by thermal evaporation on an epitaxial Ge layer on Si(100), patterned with a SiO
₂
hard mask. The patterns were then irradiated with ArF excimer laser pulses of 193 nm wavelength to induce melting and resolidification processes, aligned to the crystal structure of the Si(100) substrate below. Extensive characterization was performed, mainly using Atomic Force Microscopy and Raman Spectroscopy, examining the fabrication quality, thus the feasibility of future integrated laser devices.