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 quantumdot 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.
Electrically-pumped lasers directly grown on silicon are key devices interfacing silicon microelectronics and photonics. We report here, for the first time, an electrically-pumped, room-temperature, continuous-wave (CW) and single-mode distributed feedback (DFB) laser array fabricated in InAs/GaAs quantum-dot (QD) gain material epitaxially grown on silicon. CW threshold currents as low as 12 mA and single-mode side mode suppression ratios (SMSRs) 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±0.2 nm and exhibits a record wavelength coverage range of 100 nm, the full span of the O-band. These results indicate that, for the first time, 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.
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.
offers a low-cost solution for high-speed interconnects for data transmission. The integration of high-quality direct-bandgap III-V lasers on Si platform is a core technology for achieving high-performance Si-based III-V optoelectronic devices, [1-3] due to the inefficient light-emitting properties of Group-IV materials. [4,5] Currently, the realization of III-V lasers on Si mainly relies on either wafer bonding or monolithic growth techniques, with the latter method being more favorable for low cost, high yield and large-scale production. [6,7] Nevertheless, the large lattice mismatch, different polarities and incompatible thermal expansion coefficients between III-V materials and Si induce various crystal defects during the epitaxial growth such as threading dislocations (TDs), inversion boundaries (IBs, often called anti-phase boundaries, APBs), and microcracks. [8-13] These defects act as non-radiative recombination centers and significantly hinder the performance of optoelectronic devices in terms of lifetime, threshold operating power and temperature performance. [2,7,14] Approaches including strained-layer superlattice (SLS) acting as a defect filter layer (DFL) and a longer cool-down period after growth were implemented to sufficiently suppress TDs and micro-cracks, respectively. [12,13,15] By contrast, IBs are electrically charged planar Monolithic integration of III-V materials and devices on CMOS compatible on-axis Si (001) substrates enables a route of low-cost and high-density Si-based photonic integrated circuits. Inversion boundaries (IBs) are defects that arise from the interface between III-V materials and Si, which makes it almost impossible to produce high-quality III-V devices on Si. In this paper, a novel technique to achieve IB-free GaAs monolithically grown on on-axis Si (001) substrates by realizing the alternating straight and meandering single atomic steps on Si surface has been demonstrated without the use of double Si atomic steps, which was previously believed to be the key for IB-free III-V growth on Si. The periodic straight and meandering single atomic steps on Si surface are results of high-temperature annealing of Si buffer layer. Furthermore, an electronically pumped quantum-dot laser has been demonstrated on this IB-free GaAs/Si platform with a maximum operating temperature of 120 °C. These results can be a major step towards monolithic integration of III-V materials and devices with the mature CMOS technology.
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