We propose a new class of optoelectronic devices in which the optical properties of the active material is enhanced by strain generated from micromechanical structures. As a concrete example, we modeled the emission efficiency of strained germanium supported by a cantilever-like platform. Our simulations indicate that net optical gain is obtainable even in indirect germanium under a substrate biaxial tensile strain of about 1.75% with an electron-hole injection concentration of 9 x 10(18) cm(-3) while direct bandgap germanium becomes available at a strain of 2%. A large wavelength tuning span of 300 nm in the mid-IR range also opens up the possibility of a tunable on-chip germanium biomedical light source.

This article presents a detailed exploration of the optical characteristics of various one-dimensional photonic crystal structures designed for use as a means of improving the efficiency and power density of thermophotovoltaic ͑TPV͒ devices. The crystals being investigated have a ten-layer quarter-wave periodic structure, and are based on Si/ SiO 2 and Si/ SiON material systems. For TPV applications the crystals are designed to act as filters, transmitting photons with wavelengths below 1.78 m to a GaSb photodiode, while reflecting photons of longer wavelengths back to the source of thermal radiation. In the case of the Si/ SiO 2 structure, the Si and SiO 2 layers were designed to be 170 and 390 nm thick, respectively. This structure was fabricated using low-pressure chemical vapor deposition. Reflectance and transmittance measurements of the fabricated Si/ SiO 2 photonic crystals were taken from 0.8 to 3.3 m for both polarizations and for a range of incident angles. Measurement results were found to correlate well with simulation results for the ideal structure. Measurement results were used to predict the TPV system efficiency, power density and spectral efficiency using an ideal thermodynamic model of a TPV system.

We present a design of monolithically integrated GeSi electroabsorption modulators and photodetectors for electronic-photonic integrated circuits on a silicon-on-insulator (SOI) platform. The GeSi electroabsorption modulator is based on the Franz-Keldysh effect, and the GeSi composition is chosen for optimal performance around 1550 nm. The designed modulator device is butt-coupled to Si(core)/SiO(2)(cladding) high index contrast waveguides, and has a predicted 3 dB bandwidth of >50 GHz and an extinction ratio of 10 dB. The same device structure can also be used for a waveguide-coupled photodetector with a predicted responsivity of > 1 A/W and a 3 dB bandwidth of > 35 GHz. Use of the same GeSi composition and device structure allows efficient monolithic process integration of the modulators and the photodetectors on an SOI platform.

Articles you may be interested inGrowth kinetics and modeling of selective molecular beam epitaxial growth of GaAs ridge quantum wires on pre-patterned nonplanar substrates

Articles you may be interested inA density functional theory study of the atomic structure, formation energy, and vibrational properties of nitrogenvacancy-oxygen defects in silicon J. Appl. Phys. 108, 033513 (2010); 10.1063/1.3387912Effect of nitrogen-vacancy complex defects on the electronic transport of carbon nanotube

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We describe a Si-Ge-silica monolithic integration platform for telecommunications applications. The monolithic integration process features low-temperature silica film deposition by electron-cyclotron-resonance chemical vapor deposition to prevent thermal damage to Si/Ge active devices. The monolithically integrated Si and SiOx waveguides show propagation losses of 2.8 and 0.9 dB/cm, and the inverse-tapered spot-size converters show a coupling loss of 0.35 dB. We applied the platform to a 22-Gb/s  16-ch wavelengthdivision multiplexing receiver, in which a 16-ch SiOx arrayed waveguide grating (AWG) with 1.6-nm channel separation and Ge photodiodes (PDs) are monolithically integrated. The AWG-PD device exhibits fiber-to-PD responsivity of 0.29 A/W and interchannel crosstalk of less than À22 dB and successfully receives 22-Gb/s signal for all 16 channels. In addition, we demonstrate 40-km transmission of 12.5-Gb/s signal and obtain sensitivity of À6.8 dBm at a bit error rate of 10 À9 without transimpedance amplifiers.

The concentration of the major electron trap (0.82 eV below the conduction band) in GaAs (Bridgman grown) was found to increase with increasing As pressure during growth. It was further found that (for a given As pressure) the concentration of this trap decreased with increasing concentration of shallow donor dopants (Si, Se, and Te). Donor concentrations above a threshold of about 1017 cm−3 led to the rapid elimination of the trap. On the basis of these findings, the 0.82-eV trap was attributed to the antisite defect AsGa formed during the postgrowth cooling of the crystals.