We report the first room-temperature continuous-wave operation of III-V quantum-dot laser diodes monolithically grown on a Si substrate. Long-wavelength InAs/GaAs quantum-dot structures were fabricated on Ge-on-Si substrates. Room-temperature lasing at a wavelength of 1.28 μm has been achieved with threshold current densities of 163 A/cm² and 64.3 A/cm² under continuous-wave and pulsed conditions for ridge-waveguide lasers with as cleaved facets, respectively. The value of 64.3 A/cm² represents the lowest room-temperature threshold current density for any kind of laser on Si to date.

Monolithic integration of III-V semiconductor devices on Silicon (Si) has long been of great interest in photonic integrated circuits (PICs), as well as traditional integrated circuits (ICs), since it provides enormous potential benefits, including versatile functionality, low-cost, large-area production, and dense integration. However, the material dissimilarity between III-V and Si, such as lattice constant, coefficient of thermal expansion, and polarity, introduces a high density of various defects during the growth of III-V on Si. In order to tackle these issues, a variety of growth techniques have been developed so far, leading to the demonstration of high-quality III-V materials and optoelectronic devices monolithically grown on various Si-based platform. In this paper, the recent advances in the heteroepitaxial growth of III-V on Si substrates, particularly GaAs and InP, are discussed. After introducing the fundamental and technical challenges for III-V-on-Si heteroepitaxy, we discuss recent approaches for resolving growth issues and future direction towards monolithic integration of III-V on Si platform.

Electrically pumped lasers directly grown on silicon are key devices interfacing silicon microelectronics and photonics. We report here, for the first time, to the best of our knowledge, an electrically pumped, room-temperature, continuous-wave (CW) and single-mode distributed feedback laser array fabricated in InAs/GaAs quantum-dot gain material epitaxially grown on silicon. CW threshold currents as low as 12 mA and single-mode side mode suppression ratios as high as 50 dB have been achieved from individual devices in the array. The laser array, compatible with state-of-the-art coarse wavelength division multiplexing (CWDM) systems, has a well-aligned channel spacing of $20\pm 0.2\mathrm{nm}$ and exhibits a record wavelength covering range of 100 nm, the full span of the O-band. These results indicate that, for the first time, to the best of our knowledge, the performance of lasers epitaxially grown on silicon is elevated to a point approaching real-world CWDM applications, demonstrating the great potential of this technology.

Semiconductor III–V photonic crystal (PC) laser is regarded as a promising ultra-compact light source with unique advantages of ultralow energy consumption and small footprint for the next generation of Si-based on-chip optical interconnects. However, the significant material dissimilarities between III-V materials and Si are the fundamental roadblock for conventional monolithic III-V-on-silicon integration technology. Here, we demonstrate ultrasmall III-V PC membrane lasers monolithically grown on CMOS-compatible on-axis Si (001) substrates by using III-V quantum dots. The optically pumped InAs/GaAs quantum-dot PC lasers exhibit single-mode operation with an ultra-low threshold of ~0.6 μW and a large spontaneous emission coupling efficiency up to 18% under continuous-wave condition at room temperature. This work establishes a new route to form the basis of future monolithic light sources for high-density optical interconnects in future large-scale silicon electronic and photonic integrated circuits.