No abstract

In nanometer-size Si/SiGe-island heteroepitxial multilayers grown on Si(001), low temperature photoluminescence spectra are observed that strongly depend on the excitation wavelength and show a strong correlation with structural properties revealed by transmission electron microscopy. These experimental results can be explained by assuming that the optically created carriers are strongly localized at Si/SiGe island heterointerfaces. We show that electron-hole pairs are generated and recombine within spatial regions mainly defined by the photoexcitation penetration depth, and that the estimated exciton diffusion length is notably short and comparable with the SiGe-island average size.

We find fatigue of low temperature photoluminescence (PL) in Si/SiGe three-dimensional island morphology nanostructures under continuous excitation. Initially, the PL intensity slowly decreases by less than 15%, and after ~10 min it decreases rapidly by more than 80%. After the PL intensity stabilizes, a complete recovery requires heating the sample to nearly room temperature. We propose that accumulation of charge within SiGe islands is responsible for the enhancement of Auger recombination and hence the observed PL fatigue.

Fully integrated monolithic, multi-channel InP-based coherent receiver PICs and transceiver modules with extended C-band tunability are described. These PICs operate at 33 and 44 Gbaud per channel under dual polarization (DP) 16-QAM modulation. Fourteen-channel monolithic InP receiver PICs show integration and data rate scaling capability to operate at 44 Gbaud under DP 16-QAM modulation for combined 4.9 Tb/s total capacity. Six channel simultaneous operation of a commercial transceiver module at 33 Gbaud is demonstrated for a variety of modulation formats including DP 16-QAM for >1.2Tbit/s aggregate data capacity.

While hydrogen passivation has led to enhanced luminescence in many erbium doped materials, its effects on Er oxides/silicates compounds has rarely been demonstrated. Here we report effects of forming gas annealing on the luminescence properties in such Er compound materials. A broad band photoluminescence in the ultraviolet/visible range, likely arising from structural defects in the material, is significantly suppressed after forming gas annealing. Concurrently, the Er near-infrared luminescence intensity and its lifetime increase by about a factor of two and three, respectively. The samples are further characterized with Rutherford backscattering for composition information, optical absorption for optically excitable Er concentrations and extended x-ray absorption fine structures for Er local environments. We discuss the hydrogen passivation effects in the context of diffusion limited relaxation processes and suggest pathways to further improving near-infrared luminescence properties in Er compound materials.