Nanolasers on silicon for chip-scale optoelectronics

Scalable integration of optoelectronic devices with CMOS integrated circuits can address the growing needs for low power consumption optical interconnects, communications and signal processing. Furthermore, by augmenting electronics with optics, powerful new optoelectronic functionalities can be enabled and realized. It is well accepted that such integration should be compatible with the current CMOS infrastructure and process flows to be economically competitive. However, the high growth temperature of III-V materials places a critical roadblock on wafer-scale integration. In addition, mismatches of lattice constant and thermal expansion coefficient have fundamentally limited monolithic integration of III-V lasers onto silicon-based CMOS circuits over the past decades. In this work, we will discuss a brand new approach towards this integration using low-temperature synthesized III-V nanostructures. Excellent single-crystalline InGaAs/GaAs nanopillars and needles are grown on silicon despite of large lattice mismatches at 400C using MOCVD. We report a novel avalanche photodetectors with a high current gain and InGaAs/GaAs light emitting diodes (LEDs) with a bright electroluminescence all on Si substrates at room temperature. We report a new InGaAs nanopillar laser structure directly grown on silicon substrate, polysilicon-on-Si, and a Si substrate containing metal-oxide semiconductor field effect transistors (MOSFETs). Despite little index contrast between silicon and InGaAs, the nanopillars support helically-propagating whispering gallery modes and hence confine light strongly within a very small volume, resulting in subwavelength-sized lasers without the use of conventional plasmonic effects. In the case of nanopillar laser on MOSFET, the MOSFETs show standard transistor performance after MOCVD growth. This result demonstrates CMOS-compatibility of nano-laser growth, serving as a proof-of-concept that such integration can be extended to more complicated CMOS integ- - rated circuits. The tiny footprints of the nanolasers, combined with scalability of a new growth mechanism to produce them, make the nanopillar lasers ideal for high-density optoelectronics. Nanopillar lasers may provide the missing monolithic light sources necessary for bridging the existing gap between photonic and electronic circuits.