Continuous-wave quantum dot photonic crystal lasers grown on on-axis Si (001).

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 quantum-dot 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.

Aligned ZnO/CdTe core-shell nanocable arrays on indium tin oxide: synthesis and photoelectrochemical properties.

Vertically aligned ZnO/CdTe core-shell nanocable arrays-on-indium tin oxide (ITO) are fabricated by electrochemical deposition of CdTe on ZnO nanorod arrays in an electrolyte close to neutral pH. By adjusting the total charge quantity applied during deposition, the CdTe shell thickness can be tuned from several tens to hundreds of nanometers. The CdTe shell, which has a zinc-blende structure, is very dense and uniform both radially and along the axial direction of the nanocables, and forms an intact interface with the wurtzite ZnO nanorod core. The absorption of the CdTe shell above its band gap ( approximately 1.5 eV) and the type II band alignment between the CdTe shell and the ZnO core, respectively, demonstrated by absorption and photoluminescence measurements, make a nanocable array-on-ITO architecture a promising photoelectrode with excellent photovoltaic properties for solar energy applications. A photocurrent density of approximately 5.9 mA/cm(2) has been obtained under visible light illumination of 100 mW cm(-2) with zero bias potential (vs saturated calomel electrode). The neutral electrodeposition method can be generally used for plating CdTe on nanostructures made of different materials, which would be of interest in various applications.

Synthesis and cathodoluminescence of beta-Ga2O3 nanowires with holes.

Gallium oxide nanowires were synthesized on Si (001) substrate by chemical vapor deposition, using a Ga/Ga2O3 mixture as a precursor and Au as a catalyst. The structure of the as-synthesized products was examined by X-ray powder diffraction and high-resolution transmission electron microscopy, and found to be monoclinic beta-Ga2O3. The morphologies of the beta-Ga2O3 nanowires were characterized by scanning electron microscopy. The majority of the nanowires contain holes along their length, but a few were also found without holes. The holes are believed to be formed by the reaction of adsorbed Ga droplets on reactive terminating surfaces of the nanowires. For nanowires where these reactive surfaces are not exposed, the reaction of Ga is retarded. Cathodoluminescence (CL) of the nanowires was measured. Three emission bands centered at 376, 454, and 666 nm, respectively, were observed.