Room-temperature self-organised In0.5Ga0.5As quantum dot laser on silicon

Introduction: Future high-speed systems will, in all probability, require the monolithic integration of electronic circuits and optoelectronic components on silicon substrates. An urgent need in such technology is the development of high performance and reliable electrically-injected light sources that can be integrated on silicon in a CMOS-compatible process. Self-organised quantum dot (QD) lasers have recently exhibited superior characteristics compared to their quantum well (QW) counterparts, such as ultra-low threshold current ( Jth 100 A=cm) [1], high output power [2], extremely high temperature stability (T0 ffi1) [3], large small-signal frequency response (f 3 dB ’ 25 GHz) [4], and negligible chirp and linewidth enhancement factors [4]. The first QD laser on Si substrates, reported by Linder et al. [5], was operated at 80 K. It was found that the laser active region had substantially reduced defect densities and the dots themselves may be defect free, which was attributed to the strong strain field surrounding self-organised QDs that inhibits the propagation of dislocations through the dots. This is further confirmed by recent work of Kazi et al. [6], who showed that semiconductor lasers incorporating QD-like structures displayed higher failure resistance and improved reliability compared to similar QW lasers grown on Si substrates. In this Letter, we report the first room-temperature operation of In0.5Ga0.5As=GaAs QD lasers grown directly on Si substrates with a thin ( 2 mm) GaAs buffer layer.