Ge/SiGeSn multiple quantum well photonic devices

Active photonic devices like efficient light emitters and high speed modulators using Si and other group IV materials are difficult to realize due to indirect nature of band gap in silicon, germanium and their alloys. At present, efficient light emission has been observed by exploiting stimulated Raman scattering in silicon that needs optical pumping. An alternate route has been found recently that utilizes tensile strained Ge layer grown on SiGeSn barrier layers. The tensile strain makes the direct Avalley conduction band lower than the normal L valleys. In this paper early work on light emission in Si is briefly narrated and schemes for Raman laser are discussed. The physics behind the direct gap type I band alignment in Ge/SiGeSn multiple quantum wells is presented and work towards Ge laser are summarized. Incorporation of C in Ge makes the gap correspond to emission at 1550 nm: the standard telecommunication wavelength. The work on high speed modulators based on carrier injection/depletion is briefly reviewed. Finally principle of and progress in modulators and other devices based on quantum confined Stark effect for excitons in Avalley in Ge are introduced.