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Epitaxially integrated III–V semiconductor lasers for silicon photonics have the potential to dramatically transform information networks, but currently, dislocations limit performance and reliability even in defect-tolerant InAs quantum dot (QD)-based lasers. Despite being below the critical thickness, QD layers in these devices contain previously unexplained misfit dislocations, which facilitate non-radiative recombination. We demonstrate here that these misfit dislocations form during post-growth cooldown due to the combined effects of (1) thermal-expansion mismatch between the III–V layers and silicon and (2) mechanical hardening in the active region. By incorporating an additional sub-critical thickness, indium-alloyed "misfit dislocation trapping layer," we leverage these mechanical hardening effects to our advantage, displacing 95% of misfit dislocations from the QD layer in model structures. Unlike conventional dislocation mitigation strategies, the trapping layer reduces neither the number of threading dislocations nor the number of misfit dislocations. It simply shifts the position of misfit dislocations away from the QD layer, reducing the defects' impact on luminescence. In full lasers, adding a misfit dislocation trapping layer both above and below the QD active region displaces misfit dislocations and substantially improves performance: we measure a twofold reduction in lasing threshold currents and a greater than threefold increase in output power. Our results suggest that devices employing both traditional threading dislocation reduction techniques and optimized misfit dislocation trapping layers may finally lead to fully integrated, commercially viable silicon-based photonic integrated circuits. [ABSTRACT FROM AUTHOR]

We study the impact of misfit dislocations on the luminescence from InAs quantum dots (QDs) grown on Si substrates. Electron channeling contrast imaging is used together with cathodoluminescence mapping to locate misfit dislocations and characterize the resulting nonradiative recombination of carriers via near-infrared light emission profiles. With a 5 kV electron beam probe, the dark line defect width due to a typical misfit dislocation in a shallow QD active layer is found to be approximately 1 μm, with a 40%–50% peak emission intensity loss at room temperature. Importantly, we find that at cryogenic temperatures, the dislocations affect the QD ground state and the first excited state emission significantly less than the second excited state emission. At the same time, the dark line defect width, which partially relates to carrier diffusion in the system, is relatively constant across the temperature range of 10 K–300 K. Our results suggest that carrier dynamics in the QD wetting layer control emission intensity loss at dislocations, and that these defects reduce luminescence only at those temperatures where the probability of carriers thermalizing from the dots into the wetting layer becomes significant. We discuss the implications of these findings toward growing dislocation-tolerant, reliable quantum dot lasers on silicon. [ABSTRACT FROM AUTHOR]

We investigate, both experimentally and theoretically, the gain characteristics of modulation p-doped 1.3 μm quantum dot lasers epitaxially grown on silicon. Gain spectra and transparency points are measured for structurally identical lasers with varying levels of p doping in the active region. A many-body model is employed to facilitate understanding of the material gain characteristics. It has been found that appropriate p doping greatly reduces transparency and improves differential gain. It is also found that the improvements saturate with excessive doping because of the increase in nonradiative carrier recombination. [ABSTRACT FROM AUTHOR]

Optical frequency comb direct generation on silicon by mode locked lasers (MLLs) is promising as it offers high wavelength channel counts and ultrashort pulses that will benefit future large-scale high capacity silicon photonic integrated circuits. Here, we demonstrate two-section quantum dot (QD) MLLs that are directly grown on a complementary metal–oxide–semiconductor compatible on-axis (001) silicon substrate by employing molecular beam epitaxy. The lasers, incorporating five layers of InAs QDs, operate in the O-band wavelength range with a pulse repetition rate around 9 GHz. A pulsewidth reduction of 48% of the narrowest achievable pulse from each QD MLL is obtained when the saturable absorber (SA) section length ratio is increased from 8% to 23%. The device with the longest SA section exhibits a more than 50 dB fundamental RF peak signal to noise floor ratio with 1.3 ps pulses. [ABSTRACT FROM AUTHOR]

We demonstrate second harmonic generation in a gallium nitride photonic crystal cavity embedded in a two-dimensional free-standing photonic crystal platform on silicon. The photonic crystal nanocavity is optically pumped with a continuous-wave laser at telecom wavelengths in the transparency window of the nitride material. The harmonic generation is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second harmonic signal. The harmonic emission pattern is correlated to the harmonic polarization generated by the second-order nonlinear susceptibilities Χzxx(2), Χzyy(2) and the electric fields of the fundamental cavity mode. [ABSTRACT FROM AUTHOR]

In this letter, we present direct and unambiguous experimental evidence for nonthermal illumination effects in boron or arsenic implanted silicon. Both, dopant diffusion and activation vary significantly with illumination. Depending on annealing temperature, diffusion is either enhanced or inhibited. The results have significant implications for modeling and formation of ultrashallow junctions. [ABSTRACT FROM AUTHOR]

Negative bias temperature instabilities (NBTIs) of p-channel metal-oxide-semiconductor field-effect-transistor with HfO2, HfOxNy, and HfSiON were investigated. Higher bulk trap generation (ΔNot) is mainly attributed to threshold voltage shift rather than interface trap generation (ΔNit). ΔNit, ΔNot, activation energy (Ea), and lifetime were exacerbated with incorporated nitrogen while improved with adding Si into gate dielectrics. Compared to HfO2, HfOxNy showed worse NBTI due to nitrogen pile-up at Si interface. However, adding Si into HfOxNy placed nitrogen peak profile away from Si/oxide interface and NBTI was reduced. This improvement is ascribed to reduced ΔNot and ΔNit, resulting from less nitrogen at Si interface. [ABSTRACT FROM AUTHOR]

The continual downscaling of silicon devices for integrated circuits requires the formation of pn junctions that are progressively shallower, incorporate increasing levels of electrically active dopant, and sustain minimal implantation damage. In the case of boron implanted into preamorphized Si, the authors show that all these goals can be accomplished simultaneously through the use of an atomically clean surface, which during annealing acts as a large sink that removes Si interstitials selectively over dopant interstitials. [ABSTRACT FROM AUTHOR]

Studies the absorption of the heterofullerene C[sub 59]N on a silicon surface using scanning tunneling microscopy under ultrahigh vacuum conditions. Absorption of molecules in monomer form; Manipulation of molecules parallel and perpendicular to the dimer rows; Stability of the C[sub 59]N monomer.

Discusses the fabrication of linear arrays of CaF[sub 2] stripes and dots by self-assembly on stepped Si(111). Stripe repulsion and their counter-intuitive attachment explained via a reversal of the stacking at the CaF[sub 2]/Si(111) interface; Dot density; Application of the arrays in nanolithography.

Highly regular arrays of steps are produced on vicinal Si(111)7×7. The step edges are atomically straight for up to 2×10[sup 4] lattice sites. The terraces are single domain, which produces a minimum kink width of 2.3 nm (half a 7×7 unit cell) and thus a high barrier for creating kinks. Criteria for obtaining optimum step arrays are established, such as the miscut [approx. 1° towards (1¯1¯2)] and an annealing sequence which passes through step bunching regions quickly. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]