An electrically pumped light source on silicon is a key element needed for photonic integrated circuits on silicon. Here we report an electrically pumped AlGaInAs-silicon evanescent laser architecture where the laser cavity is defined solely by the silicon waveguide and needs no critical alignment to the III-V active material during fabrication via wafer bonding. This laser runs continuous-wave (c.w.) with a threshold of 65 mA, a maximum output power of 1.8 mW with a differential quantum efficiency of 12.7 % and a maximum operating temperature of 40 degrees C. This approach allows for 100's of lasers to be fabricated in one bonding step, making it suitable for high volume, low-cost, integration. By varying the silicon waveguide dimensions and the composition of the III-V layer, this architecture can be extended to fabricate other active devices on silicon such as optical amplifiers, modulators and photo-detectors.

Electrically pumped hybrid AlGaInAs-silicon evanescent laser

Silicon-on-insulator (SOI) wafers are precisely engineered multilayer semiconductor/dielectric structures that provide new functionality for advanced Si devices. After more than three decades of materials research and device studies, SOI wafers have entered into the mainstream of semiconductor electronics. SOI technology offers significant advantages in design, fabrication, and performance of many semiconductor circuits. It also improves prospects for extending Si devices into the nanometer region (<10 nm channel length). In this article, we discuss methods of forming SOI wafers, their physical properties, and the latest improvements in controlling the structure parameters. We also describe devices that take advantage of SOI, and consider their electrical characteristics.

Frontiers of silicon-on-insulator

It is a well-known phenomenon that two solids with sufficiently flat surfaces can stick to each other when brought into intimate contact in ambient air at room temperature. The attraction between the two bodies is primarily mediated through van der Waals forces or hydrogen bonding. Without a subsequent heating step, that type of bonding is reversible. Annealing may increase the energy of adhesion up to the cohesive strength of the materials concerned. The wafer bonding phenomena in brittle materials systems, especially in silicon, is reviewed in the experiment. The focus is on low temperature bonding techniques. The pivotal influence chemical species on the surfaces have on the subsequent type of bonding (van der Waals, hydrogen, covalent bonding, mechanical interlocking) is discussed. Methods of modifying the surface chemistry for tailoring bonding properties are addressed. The paper is aimed at providing an overview of the current understanding of the factors determining the bondability and strength of the bonding obtainable. The authors assess the present state of the experimental methods for determining basic parameters governing the adhesion. A number of examples illustrate the applicability of fusion bonding for as diverse fields as opto-electronics, microsystems technology, and fabrication of advanced substrates like silicon-on-insulator wafers.

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Wafer direct bonding: tailoring adhesion between brittle materials

Monolithic integration of III-V compound semiconductors on silicon is highly sought after for high-speed, low-power-consumption silicon photonics and low-cost, light-weight photovoltaics. Here we present a GaAs/Si direct fusion bonding technique to provide highly conductive and transparent heterojunctions by heterointerfacial band engineering in relation to doping concentrations. Metal- and oxide-free GaAs/Si ohmic heterojunctions have been formed at 300°C; sufficiently low to inhibit active material degradation. We have demonstrated 1.3 μm InAs/GaAs quantum dot lasers on Si substrates with the lowest threshold current density of any laser on Si to date, and AlGaAs/Si dual-junction solar cells, by p-GaAs/p-Si and p-GaAs/n-Si bonding, respectively. Our direct semiconductor bonding technique opens up a new pathway for realizing ultrahigh efficiency multijunction solar cells with ideal bandgap combinations that are free from lattice-match restrictions required in conventional heteroepitaxy, as well as enabling the creation of novel high performance and practical optoelectronic devices by III-V/Si hybrid integration.

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III-V/Si hybrid photonic devices by direct fusion bonding

We have fabricated photonic crystal nanocavity lasers, based on a high-quality factor design that incorporates fractional edge dislocations. Lasers with InGaAsP quantum well active material emitting at 1550 nm were optically pumped with 10 ns pulses, and lased at threshold pumping powers below 220 μW, the lowest reported for quantum-well based photonic crystal lasers, to our knowledge. Polarization characteristics and lithographic tuning properties were found to be in excellent agreement with theoretical predictions.

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Low-Threshold Photonic Crystal Laser

The Smart-Cut® process, based on ion implantation (hydrogen, helium) and wafer bonding, appears more and more as a generic process. The first part of the paper is dedicated to the specific case of thermally-induced splitting. Cavity growth by the Ostwald ripening mechanism and crack propagation are responsible for thermally-induced splitting. In this case, the splitting kinetics are controlled by hydrogen diffusion. In the second part, the latest results concerning new structures are presented.

The generic nature of SmartCut process for thin film transfer

Defectless two-dimensional photonic crystal structures have been fabricated by drilling holes in a thin multi-quantum-well InP-based heterostructure transferred onto a silicon host wafer. Extremely low group velocity modes, which correspond to the predicted photonic valence band edge, have been observed for different filling factors. Under pulsed optical pumping, room temperature laser operation around 1.5 μm has been achieved on these structures with a threshold in the milliwatt range.

InP-based two-dimensional photonic crystal on silicon: In-plane Bloch mode laser

Room temperature pulsed laser operation of 2D photonic crystal microcavities around 1.55 /spl mu/m is reported. Such devices are based on thin III/V heterostructures transferred onto silicon and include an InGaAs/InP multiquantum well (MQW) active layer.

InP 2D photonic crystal microlasers on silicon wafer: room temperature operation at 1.55 [micro sign]m

For the first time, transfer of a thin monocrystalline GaAs film from its original bulk substrate onto a silicon substrate was achieved by proton implantation and wafer bonding. Successful transfers of 3 in GaAs film are presented.

Transfer of 3 in GaAs film on silicon substrate by proton implantation process

Graphite-lattice photonic crystal structures in InP-based heterostructures transferred onto silicon, including a multi-quantum well active layer, have been designed and fabricated. 1.5 /spl mu/m vertical emission laser operation was observed at room temperature, with very low threshold (below 50 /spl mu/W).

E. Jalaguier

Papers

The generic nature of SmartCut process for thin film transfer

InP-based two-dimensional photonic crystal on silicon: In-plane Bloch mode laser

InP 2D photonic crystal microlasers on silicon wafer: room temperature operation at 1.55 [micro sign]m

Transfer of 3 in GaAs film on silicon substrate by proton implantation process

Very low threshold vertical emitting laser operation in InP graphite photonic crystal slab on silicon