III-V semiconductor nanowires (NW) are being considered as future coherent light sources for optoelectronic chips due to their small footprint and high refractive index. The 1D confinement also results in a natural Fabry-Perot resonance cavity. However, the most important feature is the feasibility of direct growth on Si platform. The research carried out in this work consists of time-resolved photoluminescence (TRPL) spectra at different optical excitation powers and temperatures for single GaAs-AlGaAs core-shell nanowire nanolasers on Silicon.
The carrier dynamics response for a single nanolaser below and above the threshold is obtained for different sets of temperatures. The lifetime corresponding to the excitation power below the threshold is of the order of hundreds of picoseconds at all low temperature intervals (4K to 60K). With increasing pump power, the decay time gets shorter until the threshold is achieved. At this point, two lifetimes are obtained for the lasing modes, one of the order of tens of picoseconds (stimulated emission) and another of the order of hundreds of picoseconds (spontaneous emission). A redshift in time-resolved spectra (2-3nm in an interval of 700ps) is measured which disappears at higher temperatures (after 60K). This redshift is a result of the change in refractive index caused by a decrease in carrier density with time. This effect disappears at higher temperatures due to the increase of non-radiative recombination.
The integration of III-V optoelectronics on Si substrates is essential for next-generation high-speed communications. The major issue in the integration of III-V semiconductor on Si is the lattice mismatch between Si and the III-V semiconductor material at the interface. The strain induced by the lattice mismatch can be relaxed when a nanostructure, such as a nanopillar (NP), is grown on Si. In this work, we experimentally determine the lasing mode by optically pumping a single InGaAs nanopillar grown on Si on insulator (SOI).
The lasing features of the InGaAs NP are characterized with different optical techniques. Power dependent photoluminescence (PL) at 7K is carried out to determine the lasing threshold by increasing the excitation power. The carrier dynamics below and above the threshold have been studied at 7K from time-resolved photoluminescence (TRPL) experiments at different excitation powers. We have measured a decrease in the carrier lifetimes with a rise in excitation power until the nanostructure starts lasing. The lifetime corresponding to the laser mode is on the order of the sensitivity of the streak camera (±1ps) indicating the extremely short laser lifetime. The InGaAs nanolaser shows a single longitudinal mode because of the small length dimensions (<1μm). The wavelength of the laser mode emission changes with each NP excited due to the slight differences in dimensions between NPs. In addition, the quality of the crystal grown has been studied with temperature-dependent PL. These results will contribute to further optimization of the InGaAs nanolaser for integration of III-V optoelectronics on Si substrates.
In this work, we study the optical properties and emission dynamics of the novel nanostructure p-GaAs nanopillars (NPs) on Si. The integration of III-V optoelectronics on Si substrates is essential for next-generation high-speed communications. NPs on Si are good candidates as gain media in monolithically integrated small-scale lasers on silicon. In order to develop this technology, an in-depth knowledge of the NP structure is necessary to resolve its optimal optical properties.
The optical characterization which has been carried out consists of the emission analysis for different NP geometries. We measured NPs with different combinations of pitch (of the order of a few μm) and diameter (of the order of tens of nm). A comparison of intensities for the various NPs provides us with the most efficient geometry. The quality of the crystal grown has been studied from temperature-dependent photoluminescence (PL). A red shift and a significant reduction of the intensity of the NP emission are observed with an increase in temperature. The results also show the presence of two non-radiative recombination channels when the intensity peaks at different temperatures are analyzed with the activation energy function.