CMOS-compatible Si⁺-implanted Si-waveguide p-i-n photodetectors operating at room temperature and at mid-infrared wavelengths from 2.2 to 2.3 µm are demonstrated. Responsivities of 9.9 ± 2.0 mA/W are measured at a 5 V reverse bias with an estimated internal quantum efficiency of 2.7 - 4.5%. The dark current is found to vary from a few microamps down to less than a nanoamp after a post-implantation annealing of 350°C. The measured photocurrent dependence on input power shows a linear correspondence over more than three decades, and the frequency response of a 250 µm-length p-i-n device is measured to be ~1.7 GHz for a wavelength of λ = 2.2 µm, thus potentially opening up new communication bands for photonic integrated circuits.

Imaging micro-Raman spectroscopy is used to investigate the materials physics of radiation damage in congruent LiNbO 3 as a result of high-energy (~MeV) He + irradiation. This study uses a scanning confocal microscope for high-resolution three-dimensional micro-Raman imaging along with reflection optical microscopy (OM), and scanning electron microscopy (SEM). The tight optical excitation beam in the Raman system allows spatial mapping of the Raman spectra both laterally and normal to the irradiation axis with ≤1 μm resolution. Point defects and compositional changes after irradiation and surface deformation including blistering and microstress are observed in the stopping region. We demonstrate that the probed area of the damaged region is effectively "expanded" by a beveled geometry, formed through off-angle polishing of a crystal facet; this technique enables higher-resolution probing of the ion-induced changes in the Raman spectra and imaging of dislocation line defects that are otherwise inaccessible by conventional probing (depth and edge scan). Twodimensional (2D) Raman imaging is also used to determine the defect uniformity across an irradiated sample and to examine the damage on a sample with patterned implantation. The effects of different He + doses and energies, together with post-irradiation treatments such as annealing, are also discussed.

Articles you may be interested inFabrication of high quality factor photonic crystal microcavities in In As P ∕ In P membranes combining reactive ion beam etching and reactive ion etching Broad ion beam milling of focused ion beam prepared transmission electron microscopy cross sections for high resolution electron microscopy Side-wall damage in a transmission electron microscopy specimen of crystalline Si prepared by focused ion beam etching Optimization of experimental operating parameters for very high resolution focused ion beam applicationsCommonly used preparation method for thin diamond membranes by focused ion beam (FIB) techniques results in surface damage. Here, the authors introduce an alternative method based on reactive ion etching (RIE). To compare these methods, cross-sectional samples are produced in single crystal diamond, a material that has generated growing interest for a variety of applications. The samples are examined by Raman spectroscopy and high-resolution transmission electron microscopy (TEM). Raman spectra indicate that the crystalline structure of the RIE-processed diamond is preserved, while the FIB-processed diamond membrane has a broad-background sp 2 feature. Atomic-resolution TEM imaging demonstrates that the RIE-based process produces no detectable damage, while the FIB-processed sample has an amorphous carbon layer of about 11 nm thick. These findings show that the RIE-based process allows the production of diamond TEM samples with reduced near-surface damage and can thus enable direct examination of growth defects and crystallographic damage induced by processes such as ion implantation and bombardment.

Scanning micro-Raman spectroscopy has been utilized to image and investigate strain in He +-implanted congruent LiNbO 3 samples. By using abruptly patterned implanted samples, we show that the spatial twodimensional mapping of the Raman spectral peaks can be used to image the strain distribution and determine its absolute magnitude. We demonstrate that both short-and long-range length-scale in-plane and out-of-plane strain and stress states can be determined using the secular equations of phonondeformation-potential theory. We also show that two-dimensional Raman imaging can be used to visualize the relaxation of strain in the crystal during low-temperature annealing.

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