Continuous-wave lasing from InP/InGaAs nanoridges at telecommunication wavelengths

We report continuous-wave lasing from InP/InGaAs nanoridges grown on a patterned (001) Si substrate by aspect ratio trapping. Multi-InGaAs ridge quantum wells inside InP nanoridges are designed as active gain materials for emission in the 1500 nm band. The good crystalline quality and optical property of the InGaAs quantum wells are attested by transmission electron microscopy and microphotoluminescence measurements. After transfer of the InP/InGaAs nanoridges onto a SiO2/Si substrate, amplified Fabry-Perot resonant modes at room temperature and multi-mode lasing behavior in the 1400 nm band under continuous-wave optical pumping at 4.5 K are observed. This result thus marks an important step towards integrating InP/InGaAs nanolasers directly grown on microelectronic standard (001) Si substrates. Semiconductor nanowires are emerging as ideal building blocks for ultra-compact optoelectronic devices with low-energy dissipation.1 As a result of axially guided optical modes and feedback provided by end-facets, lasing behaviors have been observed in various II-VI and III-V compound semiconductor nanostructures.2–16 In particular, indium phosphide (InP) and indium gallium arsenide (InGaAs) nanolasers, emitting at silicon(Si)-transparent wavelengths, show great promise to fill a key missing on-chip component in Si photonic-based optical interconnects.17–21 However, most of the previously demonstrated InP/InGaAs nanolasers operate under pulsed-conditions.22–24 Continuous-wave (CW) lasing at telecom wavelengths has only been achieved in InP/InGaAs nanopillars grown on (111) Si substrates25 and InAsP/InP nanowires (inside Si photonic crystal cavity) grown on (111)B InP substrates, with lasing wavelengths situated at the 1200 and 1300 nm bands.26 Extending the lasing wavelengths to the 1400 nm and 1500 nm bands is desirable for high density inter/intra-chip data transmission. In this letter, we utilized InP/InGaAs nanoridges grown on a (001) Si substrate to demonstrate CW lasing behavior at the 1400 nm band. Compared with other hetero-epitaxial growth techniques, selective area growth combined with the aspect ratio trapping (ART) method provides a viable route to form well-aligned, millimeter-long horizontal in-plane nanowires on CMOS-standard (001) Si substrates.27–34 Previously, we have leveraged this approach to grow InP nanoridges with embedded InGaAs quantum wells (QWs) and quasi-quantum wires (QWRs) with strong photolumiescence.35,36 Here, we observe CW lasing at the telecommunication band from high quality multi-InGaAs ridge QWs inside the InP nanoridges directly grown on nanopatterned silicon. To explore the potential of the InP/InGaAs nanoridges as nanoscale light sources, we separated the InP/InGaAs nanoridges from the initial patterned Si substrate and transferred them onto a SiO2/Si substrate for optical characterization. We observed CW lasing at 4.5 K under optical excitation and strong optical mode modulation at room temperature. The InP/InGaAs nanoridges used in this experiment were grown on (001) Si substrates using a metal-organic chemical vapor deposition (MOCVD) system with a horizontal reactor (AIXTRON 200/4). [110] direction oriented SiO2 stripe patterns with a line pitch of 1 μm and a trench opening width of 450 nm were used to define the growth regions. Detailed sample preparation and the growth procedure have been reported elsewhere.35,36 Figure 1(a) presents the top-view scanning electron microscopy (SEM) image of the as-grown sample, showing a uniform morphology across a large area. The 70° tilted-view SEM image in Fig. 1(b) reveals symmetrical {111} faceting. A zoomed-in SEM image in Fig. 1(c) highlights the multi-QW active region. Notably, to enhance contrast, the InGaAs layers were selectively etched in a H2PO4:H2O2:H2O (3:1:50) solution. Five uniform InGaAs ridge QWs and the GaAs nucleation buffer are clearly identified