The authors report lasing of InAs∕InGaAsP∕InP (100) quantum dots (QDs) wavelength tuned into the 1.55μm telecom region. Wavelength control of the InAs QDs in an InGaAsP∕InP waveguide is based on the suppression of As∕P exchange through ultrathin GaAs interlayers. The narrow ridge-waveguide QD lasers operate in continuous wave mode at room temperature on the QD ground state transition. The low threshold current density of 580A∕cm2 and low transparency current density of 6A∕cm2 per QD layer, measured in pulsed mode, are accompanied by low loss and high gain with an 80-nm-wide gain spectrum.

Low temperature (675 °C) epitaxial in situ doped Si layers (As, 1.5 at. %) were analyzed by atom probe tomography (APT) to study clustering in a highly arsenic-doped silicon layer. The spatial distribution of As atoms in this layer was obtained by APT, and the distance distribution between first nearest neighbors between As atoms was studied. The result shows that the distribution of As atoms is nonhomogeneous, indicating clustering. Those clusters, homogeneously distributed in the volume, are found to be very small (a few atoms) with a high number density and contain more than 60% of the total number of As atoms.

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