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Monolithic integration of III-V quantum dot (QD) lasers onto a Si substrate is a scalable and reliable approach for obtaining highly efficient light sources for Si photonics. Recently, a combination of optimized GaAs buffers and QD gain materials resulted in monolithically integrated butt-coupled lasers on Si. However, the use of thick GaAs buffers up to 3 μm not only hinders accurate vertical alignment to the Si optical waveguide but also imposes considerable growth costs and time constraints. Here, for the first time, we demonstrate InAs QD lasers epitaxially grown on a 700 nm thick GaAs/Si template, which is approximately four times thinner than the conventional III-V buffers on Si. The optimized 700 nm GaAs buffer yields a remarkably smooth surface and low threading dislocation density of 4 × 10 8 cm -2 , which is sufficient for QD laser growth. The InAs QD lasers fabricated on these ultrathin templates still lase at room temperature with a threshold current density of 661 A/cm 2 and a characteristic temperature of 50 K. We believe that these results are important for the monolithically integrated III-V QD lasers for Si photonics applications.

In this report, we measured experimentally the modal absorption spectra of the InP and InAsP quantum dot (QD) lasers using multi-section device technique. The optical absorption cross section ( σ 0 ) and inhomogeneous broadening for the ground state (GS) and excited state (ES) were analyzed and calculated theoretically from the absorption spectra. The results showed that the InP QD laser exhibited σ 0 to be 1.347 × 10 - 14  ​cm 2 . eV and 3.016 × 10 - 14  ​cm 2 eV for GS and ES respectively, whereas for the InAsP QD material it was found as 0.511 × 10 - 14 cm 2 eV and 3.099 × 10 - 14 cm 2 . eV for GS and ES respectively. Moreover, the inhomogeneous broadening in the GS increases from 35.6 eV to 63.6 eV when As was added to InP QD, similarly, the inhomogeneous broadening of ES increases from 46.9 eV to 103.8 eV. The alloying InP QDs with arsenic decreases the σ 0 of the ground state (lasing state) and increases both inhomogeneous and linewidth broadenings. This finding may help the grower to control the growth conditions and the molecule fractions of the crystal to improve the spectral properties of the optoelectronics devices., Competing Interests: The authors declare no conflict of interest., (© 2022 The Author(s).)