Reliable, efficient electrically pumped silicon-based lasers would enable full integration of photonic and electronic circuits, but have previously only been realized by wafer bonding. Here, we demonstrate the first continuous-wave InAs/GaAs quantum-dot lasers directly grown on silicon substrates with a low threshold current density of 62.5 A/cm 2 , a room-temperature output power exceeding 105 mW, lasing operation up to 120 o C, and over 3,100 hours of continuous-wave operating data collected, giving an extrapolated mean time to failure of over 100,158 hours. The realization of highperformance quantum-dot lasers on silicon is due to the achievement of a low density of threading dislocations on the order of 10 5 cm -2 in the III-V epilayers by combining a nucleation layer and dislocation filter layers with in-situ thermal annealing. These results are a major advance towards silicon-based photonics and photonic-electronic integration, and could provide a route towards reliable and cost-effective monolithic integration of III-V devices on silicon.Increased data throughput between silicon processors in modern information processing demands unprecedented bandwidth and low power consumption beyond the capability of conventional copper interconnects. To meet these requirements, silicon photonics has been under intensive study in recent years 1,2 . Despite rapid progress being made in silicon-based light modulation and detection technology and low-cost silicon optoelectronic integrated devices enabled by the mature CMOS technology 3,4 , an efficient reliable electrically pumped laser on a silicon substrate has remained an unrealized scientific challenge 5 . Group IV semiconductors widely used in integrated circuits, e.g. silicon and germanium, are inefficient light-emitting materials due to their indirect bandgap, introducing a major barrier to the development of silicon photonics. Integration of IIIÐV materials on a silicon platform has been one of the most promising techniques for generating coherent light on silicon. IIIÐV semiconductors with superior optical properties, acting as optical gain media, can be either bonded or epitaxially grown on silicon substrates [6][7][8][9][10][11] , with the latter approach being more attractive for large scale, low-cost, and streamlined fabrication. However, until now, material lattice mismatch and incompatible thermal expansion coefficients between IIIÐV materials and silicon substrates have fundamentally limited the monolithic growth of IIIÐV lasers on silicon substrates by introducing high-density threading dislocations (TDs) 12 .Lasers with active regions formed from III-V quantum dots (QDs), nano-size crystals, can not only offer low threshold current density (J th ) but also reduced temperature sensitivity [13][14][15][16][17] . As shown in Figure 1a, within less than 10 years, the performance of QD lasers has surpassed state-of-the-art quantum-well (QW) lasers developed over the last few decades in terms of J th . QD lasers have now been demonstrated with nearly constan...

High-performance III-V quantum-dot lasers monolithically grown on Si substrates have been demonstrated as a promising solution to realise Si-based laser sources with very low threshold current density, high output power and long lifetime, even with relatively high density of defects due to the material dissimilarities between III-Vs and Si. On the other hand, although conventional III-V quantum-well lasers grown on Si have been demonstrated after great efforts worldwide for more than 40 years, their practicality is still a great challenge because of their very high threshold current density and very short lifetime. However, the physical mechanisms behind the superior performance of silicon-based III-V quantum-dot lasers remain unclear. In this paper, we directly compare the performance of a quantum-well and a quantum-dot laser monolithically grown on on-axis Si (001) substrates, both experimentally and theoretically, under the impact of the same density of threading dislocations. A quantum-dot laser grown on a Si substrate with a high operating temperature (105 °C) has been demonstrated with a low threshold current density of 173 A/cm 2 and a high single facet output power >100 mW at room temperature, while there is no lasing operation for the quantum-well device at room temperature even at high injection levels. By using a rate equation travelling-wave model, the quantum-dot laser's superior performance compared with its quantum well-based counterpart on Si is theoretically explained in terms of the unique properties of quantum dots, i.e., efficient carrier capture and high thermal energy barriers preventing the carriers from migrating into defect states.

We report the first demonstration of gain-switched optical pulses generated by continuous-wave 1.3 μm InAs/GaAs quantum dot (QD) broad-area lasers directly grown on silicon (Si). The shortest observed pulses have typical durations between 175 ps and 200 ps with peak output powers of up to 66 mW. By varying the drive current pulse width and amplitude systematically, we find that the peak optical power is maximized through sufficiently long high-amplitude drive pulses, whereas shorter drive pulses with high amplitudes yield the narrowest achievable pulses. A three-level rate equation travelling wave model is used for the simulation of our results in order to gain a first insight into the underlying physics and the laser parameters responsible for the observed behavior. The simulations indicate that limited gain from the InAs quantum dots and a very high gain compression factor are the main factors contributing to the increased pulse width. As the optical spectra of the tested broad-area QD laser give clear evidence of multi-transverse mode operation, the laser's dynamic response could be additionally limited due to transversal variations of the gain, carrier density, and photon density over the 50 μm wide laser waveguide.

A nanocomposite Ni–B/Ga(As)Ox/GaAs photoanode fabricated by combining molecular beam epitaxy with in situ photoassisted electrodeposition enables efficient and stable photoelectrochemical water splitting.

In this work, we give a direct interpretation of micrographs of the 60 and 90 defect core at the GaAs/Si interface using aberration corrected scanning transmission electron microscopy. We investigate the post-growth annealing effects on dislocation rearrangement at the interface as well as the threading dislocations in buffer layers; finally, the density of threading dislocations has been calculated as a function of annealing temperature.