Vertical Facets Research Articles

Continuous‐Wave Operation of 457 nm InGaN Laser Diodes with Etched Facet Mirrors for On‐Chip Photonics

The success of silicon photonics is sparking widespread interest in photonic integrated circuits at visible light wavelengths using SiN and other waveguiding platforms. Compact active circuits desire the heterogeneous integration of GaN‐based laser diodes. Herein, the optimization of smooth and vertical facets is reported using a combination of inductively coupled plasma etching followed by wet etching with a tetramethylammonium hydroxide‐based solution. Facet quality for concave‐, flat‐, and convex‐shaped structures surrounding the mirror is compared. Convex‐shaped structures result in the highest facet quality due to the evolution of the crystal plane‐dependent etching. 2 μm‐wide ridge waveguide, etched facet Fabry–Pérot cavity lasers with length of 1.5 mm emitting at 457 nm are realized using the optimized process. The lasers deliver up to 28 mW of optical power at 250 mA under continuous wave with slope efficiency of 0.26 W A−1 and lasing threshold current density of 4.6 kA cm−2.

High power GaSb-based superluminescent diode with cascade cavity suppression waveguide geometry and ultra-low antireflection coating

We report on a GaSb-based superluminescent diode optimized for high-power broadband operation around a wavelength of 2 μm. The high optical power was achieved by the high-quality epitaxial InGaSb/AlGaAsSb type-I quantum well gain material, which was processed into a double-pass amplification configuration. To prevent lasing at high current injection while enabling strong amplified spontaneous emission, a cascade cavity suppression waveguide geometry was designed to connect the vertical rear facet with the reflectivity-suppressed angled front facet. A Ta2O5/SiO2 ultra-low antireflection coating with a minimum reflectivity of 0.04% was applied to the front facet for further cavity suppression. This combination allowed the superluminescent diodes to demonstrate a record high single-transverse-mode output power of up to 152 mW under continuous-wave operation at room temperature, with a broad spectral band of 42 nm full width at half maximum. A 25% promotion in optical power has been realized compared to current state-of-the-art devices in this wavelength range, without sacrificing spectral bandwidth. The high-power spectral density characteristics, along with a good beam quality, are well suited for absorption spectroscopy applications and hybrid integration with silicon technology.

The Facets of Social Hierarchy: How Judges’ Legitimacy Beliefs and Relative Status Shape Their Evaluation of Assertiveness and Ability

Contemporary approaches of impression formation and stereotypes celebrate the role of the Big Two in social evaluation: the horizontal and vertical dimensions (Abele et al., 2021). Recently, interest has grown in making further distinctions within each of these dimensions (Abele et al., 2008). Here, we focused on the vertical facets, namely, assertiveness and ability. Research found that assertiveness is more strongly related to a target’s status than ability. Arguably, this pattern emerges because assertiveness comes across as less negotiable, whereas ability leaves more room for appreciation. Building on this assumption, we reasoned that judgments of ability provide more opportunity to justify or to reclaim positive identity, depending on one’s position in the hierarchy. Specifically, we hypothesized that the legitimacy beliefs and status of the judges are key factors to consider in that they moderate the perceived overlap between the vertical facets. Using a novel paradigm based on Goodman et al.’s (2001) social ladder, Studies 1a and 1b relied on judges’ legitimacy beliefs as a proxy for status, whereas Studies 2 and 3 directly examined the judges’ relative status. As predicted, we consistently found more overlap between assertiveness and ability among high-legitimacy/status judges than among low-legitimacy/status judges. We discuss the importance of taking into account the more specific meaning of the facets.

Evaluation of the Self on the Big Two and their Facets: Exploring the Model and its Nomological Network

Social evaluation of the self, of others, and of groups rests on two dimensions, also called ‘the Big Two’ (Horizontal: Communion, Warmth; Vertical: Agency, Competence). These Big Two have recently been broken down into two facets each. The Vertical dimension comprises Ability and Assertiveness, the Horizontal dimension Friendliness and Morality (Abele et al., 2008,2016,2021). In three studies, the present paper further explores this dimensions/facets conceptualization. We ask if the facets add explanatory power over and above the dimensions; and we analyze a number of criterion variables not considered before. Participants always had to rate themselves on the dimensions/facets and answered additional measures. These were social desirable responding and item valence. These are interesting from a methodological point of view. Self-efficacy and dominance orientation (vertical facets) and social value orientation (horizontal facets) were of interest with respect to the distinction of the facets. Finally, life satisfaction and self-awareness were analyzed as more remote constructs. Findings supported the dimension/facets model; they supported the construct validity of the Big Two; they supported the construct validity of the facets; and they revealed instances, under which distinguishing between the facets is promising. Further research perspectives regarding targets of evaluation and regarding construct validity particularly of the Horizontal facets are outlined. We summarize that the facet conceptualization is an important extension of the prominent Big Two approach.

Simple reformulation of the coordinate transformation method for gratings with a vertical facet or overhanging profile.

We reformulate the coordinate transformation method (C method) for gratings with a vertical facet or overhanging profile (overhanging gratings), in which no tensor concept is involved, only the knowledge of elementary mathematics and Maxwell's equations in the rectangular coordinate system is used, and we provide a detailed recipe for programming. This formulation is easy to understand and implement. It adopts the strategy of a rotating coordinate system from Plumey et al. [J. Opt. Soc. Am. A14, 610 (1997)JOAOD60740-323210.1364/JOSAA.14.000610] and expresses it with the method of changing variables from Li et al. [Appl. Opt.38, 304 (1999)APOPAI0003-693510.1364/AO.38.000304]. We investigate several typical overhanging gratings by the reformulated C method, and we validate and compare the results with the Fourier modal method, which shows that it is superior, especially for metal deep smooth gratings. This reformulation can facilitate the research in light couplers for optical engineers.

Bi4O5Br2 nanosheets with vertical aligned facets for efficient visible-light-driven photodegradation of BPA

Enhancing spatial charge separation efficiency through directional charge transfer is one of the vital strategies to improve the photocatalytic performances. Bi4O5Br2 nanosheets with vertical aligned (11−3), (32−2), and (112) facets were constructed to achieve the efficient directional charge transfer and separation based on the distinctive electronic and band structures of different facets. That is, the photoexcited electrons migrate to the top surface of (11−3) facet of the Bi4O5Br2 nanosheets, while the holes transfer to the lateral surface of (32−2) and (112) facets. As a result, such Bi4O5Br2 nanosheets with vertical aligned facets has highly strengthened the visible-light photodegradation efficiency of bisphenol A (BPA), which is around 6 times higher than that of BiOBr nanosheets. This work provides new sight to rational design the facets of photocatalysts for effective separation of charge carriers and promoted photocatalytic performances.

3D-printed optical probes for wafer-level testing of photonic integrated circuits.

Wafer-level probing of photonic integrated circuits is key to reliable process control and efficient performance assessment in advanced production workflows. In recent years, optical probing of surface-coupled devices such as vertical-cavity lasers, top-illuminated photodiodes, or silicon photonic circuits with surface-emitting grating couplers has seen great progress. In contrast to that, wafer-level probing of edge-emitting devices with hard-to-access vertical facets at the sidewalls of deep-etched dicing trenches still represents a major challenge. In this paper, we address this challenge by introducing a novel concept of optical probes based on 3D-printed freeform coupling elements that fit into deep-etched dicing trenches on the wafer surface. Exploiting the design freedom and the precision of two-photon laser lithography, the coupling elements can be adapted to a wide variety of mode-field sizes. We experimentally demonstrate the viability of the approach by coupling light to edge-emitting waveguides on different integration platforms such as silicon photonics (SiP), silicon nitride (TriPleX), and indium phosphide (InP). Achieving losses down to 1.9 dB per coupling interface, we believe that 3D-printed coupling elements represent a key step towards highly reproducible wafer-level testing of edge-coupled photonic integrated circuits.

Selective-Area Growth of AlInAs Nanowires

High performance transistors are required for the beyond CMOS in terms of low drive voltage, high drain current, high ION/IOFF ratio, and scalability. A superlattice (SL) resonance tunneling field-effect transistor (RTFET) achieves a steep subthreshold slope (SS < 60 mV/decade) while enhancing drain currents with high ION/IOFF ratio as compared with conventional TFETs [1]. However, the difficulty remains in forming high quality SL with various lattice mismatched system. NW structures enable us to maintain lattice strain and increase the critical thickness as compared with planar structures [2]. Thus, NWs can avoid formation of the misfit dislocations in highly lattice mismatched systems. In addition, vertical NWs are suitable for the vertical gate-all-around FETs (VGAA-FETs), which have superior scalability as compared with lateral FETs [3]. The lattice mismatched InGaAs/AlInAs SL is promising candidate for the RTFET [1]. There are, however, no insights regarding nanometer-scaled selective-area growth of AlInAs. Here, we characterized the selective-area growth of AlInAs NWs for the InGaAs/AlInAs NW RTFETs.AlxIn1-xAs NWs were grown by selective-area MOVPE. First, 20-nm-thick SiO2 film was formed on InP(111)B substrates by RF sputtering. Mask openings with various opening diameter (Dop: 50 - 160 nm) and pitch (Pop: 350 - 1000 nm) were formed using the electron beam lithography, dry and wet chemical etching. Next, AlxIn1-xAs was grown in a horizontal MOVPE systems with working pressure of 0.1 atm. Trimethylindium (TMIn), trimethylaluminum (TMAl), arsine (AsH3), and tertiarybutylphosphine (TBP) were used as source precursors. The growth temperature (TG) were varied from 550°C to 650°C. Al composition PAl (PAl = [TMAl] / [TMIn]+[TMAl]) in the vapor phase was changed from 0 to 30%. The partial pressure V/III ratio and growth time (t) were constant (V/III: 411, t: 12 min).Figure 1 shows results of selective-area growth of AlInAs with various PAl. Figure 2 exhibits the TG dependence of the AlInAs growths at PAl = 30%. Pop was 350 nm. Figure 3 shows average height of the NWs with the variation of the NW diameter with respect to PAl [Fig.3(a)] and TG [Fig. 3(b)]. As shown in Fig.1, the NWs had hexagonal pillars surrounded with the {-110} vertical facets and the (111)B plane. The lateral over growth along the <-110> directions were enhanced with increasing the PAl, while vertical NW growth along the <111>B direction was suppressed. The volume of the NWs was also decreased as shown in Fig. 3 (a), meaning that Al atoms disturbed surface diffusion of In atoms on NW sidewalls and SiO2 mask. Since the In atoms rarely reach on the top of the (111)B plane of the NWs under high PAl, the volume of the NWs was decreased. Figure 2 indicated that some AlInAs abnormal deposition occurred on the SiO2 mask at TG = 620°C. In Fig. 3 (b), the volume of the NWs was decreased with increasing TG, and eventually {-110} vertical flat facets disappeared at TG = 650°C, as shown in Fig. 2. This was because that the desorption process of group-III atoms was dominant at high TG. Thus, the optimum TG window to suppress the lateral over growth was thought to be in between 620°C and 650°C at the PAl. After the growth, NWs were etched to characterize Dop and the lateral over growth rate. We determined the diameter difference between the average DNW and Dop as Δdiameter. Figure. 4 shows the Δdiameter as a function of PAl or TG (Pop = 350 nm). In Fig. 4(a), the Δdiameter was gradually increased with PAl,,and, especially, was rapidly enhanced at PAl = 30%, while the NW volume was decreased. This indicated that the Al atoms enhanced the absorption of In atoms on the {-110} sidewalls under higher PAl. In Fig. 4(b) at PAl = 30%, the lateral over growth rate was decreased with increasing TG. Simultaneously, the volume of the grown AlInAs was rapidly decreased. Similar properties were observed in case of PAl = 20%. This indicated that the desorption process became dominant at higher TG. Further characterization of the growth mechanism for the selective-area growth of AlInAs will be presented.

The occupational attractiveness of the built environment and the roles of individualism and collectivism: a hidden source of conflict and gender imbalance?

The success of built environment projects is closely dependent on strong collective cooperation. Yet abundant anecdotal and academic evidence attests to weak collective cooperation within the industry. To date, no research in the built environment has investigated either the individual-level differences in individualism/collectivism that affect cooperativeness, or how gender may interact with these individual-level traits. In this research we seek to make a positive contribution by using the individual rather than organization as the unit of analysis. We first test the possibility that the built environment may in fact attract uncooperative individuals who are more individualistic than collectivist with respect to two specimen subsectors, i.e. construction management and architecture. At the same time we also employ a nuanced distinction between horizontal and vertical facets of individualism/collectivism, and assess potential interactions with gender. Using individual-level data (N=548), we find that both the architecture and construction management subsectors are occupationally attractive to individuals from opposing ends of the horizontal and vertical individualism/collectivism spectrums, and that these traits interact with gender. We argue that our findings both expose an individual-level source of poor collective cooperation in the built environment industry, and underscore the need to address persistently low female recruitment and retention rates.

Tailored Hydrothermal Synthesis of Specific Facet-Dominated TiO2 Nanocrystals from Lepidocrocite-Type Layered Titanate Nanosheets: Systematical Investigation and Enhanced Photocatalytic Performance

A series of samples including leaf-like and rod-like rutile TiO2 nanoparticles with various facets exposed on the surface, parallelepiped-shaped anatase nanoparticles with [111] vertical facet exposed on the surface, irregular anatase nanoparticles, microsized six-point star-like anatase aggregates, and almond-like brookite aggregates had been hydrothermally synthesized from lepidocrocite-type layered titanate nanosheets. A systematical investigation was established to uncover the phase transition and morphological evolution from nanosheets to TiO2 polymorphs, and a phase diagram was determined by adjusting the synthesis parameters of the pH value and temperature. Two kinds of mechanisms composed of the dissolution-deposition process following Ostwald's ripening mechanism and the in situ topochemical conversion process following Ostwald's step rule had been proposed based on the time-dependent hydrothermal experiments. Briefly, the formation of the single-crystalline rutile phase appeared only at high temperatures with very low pH values, and similarly, the brookite phase strictly formed at high temperatures with a very high pH value. Nevertheless, the anatase phase could moderately appear in a wide range of temperatures and pH values. In addition, the single-crystalline rutile adopted a leaf-like morphology at low temperatures with high pH values and a rod-like morphology at high temperatures with low pH values, while the morphological evolution of anatase particles proceeded from irregular to parallelepiped-shaped and finally to six-point star-like morphology, and the crystal size was reduced from 1000 to 5 nm with decreasing pH values. Meanwhile, with the prolongation of the hydrothermal time, the layered titanate nanosheets first dissolved into the amorphous state and further converted into small anatase nanoparticles and finally to rutile or anatase nanoparticles based on the dissolution-deposition process, or the {010}-faceted layered titanate structure first converted into the [111]-vertical faceted anatase nanosheets by the topochemical transformation reaction and then split into the [111]-vertical faceted anatase nanoparticles. More importantly, the mesoporous [111]-vertical faceted anatase nanoparticles exhibited enhanced photocatalytic performance compared to that of Degussa P25, which was ascribed to its superior electronic band structure and effective charge separation. The systematical investigation in this work would be significant for consummating the preparation of the TiO2 polymorphs from layered titanate nanosheets and provided some reference values and guide schemes for the preparation of TiO2 nanoparticles with outstanding photocatalytic performance.

In-situ liquid cell TEM investigation on assembly and symmetry transformation of Pt superlattice

Two dimensional (2D) nanocrystal functional superlattices with a well controlled structure are of significant importance in photonic, plasmonic and optoelectronic applications and have been well studied, but it remains challenging to understand the formation mechanism and development pathway of the superlattice. In this study, we employed in-situ liquid cell transmission electron microscopy to study the formation of 2D superlattice and its local phase transition from hexagonal-to-square nanocrystal ordering. When colloidal nanocrystals flowed in the solution, long-range ordered hexagonal superlattice could be formed either through shrinking and rearrangement of nanocrystal aggregates or via nanocrystal attachment. As the nanocrystals’ shape transformed from truncated octahedral to cube, the local superlattice rearranged to square geometry. Moreover, our observations and quantitative analyses reveal that the phase transition from hexagonal to square mainly originates from the strong van der Waals interactions between the vertical (100) facets. The tracking of 2D cube superlattice formation in real-time could provide unique insights on the governing force of superlattice assembling and stabilization.

Usefulness of 3D Printed Models in the Management of Complex Craniovertebral Junction Anomalies: Choice of Treatment Strategy, Design of Screw Trajectory, and Protection of Vertebral Artery

To evaluate the usefulness of 3-dimensional (3D) printed models as an aid for the treatment of complex CVJ anomalies. 3D printed models were fabricated for 21 patients with complex CVJ anomalies, including vertebral artery anomaly, thin C2 pedicle, vertical atlantoaxial facet joint, or rotational dislocation combined with atlantoaxial dislocation and basilar invagination. Preoperative planning, surgical simulation, and intraoperative reference were achieved using the 3D model during the surgical treatment. The usefulness of 3D printed models, and postoperative clinical and radiological outcomes were assessed. Direct posterior reduction and atlantoaxial fixation were achieved in 19 patients. Transoral odontoidectomy followed by posterior fixation was implemented for 2 patients with vertical facet joint and rotational dislocation. All screws were safely inserted with no complication, and 90% patients achieved a >60% reduction of both horizontal and vertical dislocation. Clinical symptoms improved in all patients, with the averaged Japanese Orthopedic Association scores increasing from 11.14 to 14.43 (P < 0.01). The patient-specific 3D printed model would be an effective tool for evaluation of the reducibility of the atlantoaxial dislocation and basilar invagination, decision making in choosing the optimal surgical approach and way of fixation, and precise placement of the screw while protecting the vertebral artery and spinal cord. The risk of neurovascular injury was minimized, and encouraging outcomes were achieved with the aid of this technique.

Fermi surface nesting and intrinsic resistivity of beryllium: First-principles calculations

Within the semiclassical Boltzmann transport theory, we perform a systematic first-principles calculation of the intrinsic resistivity of beryllium, a nodal-line semimetal. The Wannier interpolation technique to treat the electron-phonon ($e$-ph) interaction is employed to guarantee a high precision of the numerical results. Our numerical results of the intrinsic resistivity of beryllium agree quantitatively with experimental data in a large temperature range. We find that around each joint region between the electron and hole pockets, the Fermi surface of beryllium forms a pair of vertical facets (parallel to $c$ axis). Then, the nesting effect between such Fermi surface segments near inequivalent vertices of the hexagonal Brillouin zone can be realized by $e$-ph scattering with a relatively short phonon wavelength. Such a Fermi surface nesting effect plays the dominant role in the intrinsic resistivity. It is also the underlying mechanism for linear temperature dependence of the intrinsic resistivity from a very low critical temperature (200 K). In contrast, the contribution of the topological nontrivial states near the nodal line to the intrinsic resistivity is less important because only a few of such states appear in the vicinity of the Fermi surface due to the sizable dispersion of the nodal line.

AUTOMATIC ROAD STRUCTURE DETECTION AND VECTORIZATION USING MLS POINT CLOUDS

Abstract. Accurate three-dimensional road structures and models are of great significance to intelligent transportation applications, such as vehicle navigation, inventory evaluation, construction quality control, self-driving vehicles and so on. This paper proposes an efficient and robust method to automatically extract structured road curbs from mobile laser scanning (MLS) data. The proposed method mainly consists of three steps: efficient supervoxel generation, road curbs detection and driving free space estimation. First, supervoxels are generated by assigning ground points with similar geometrical characteristics into the same group. Second, supervoxels with higher local projection density and height difference are identified and clustered as initial road curbs, which are continuous vertical curb facets. The continuous facades consisting of lots of scanned points on the road shoulder can be modeled as multi-dimensional boundary models depending on the requirements of the application, such as vector lines with or without height, micro-facades, etc. Finally, driving free space is obtained due to the road limits can be defined by road boundary in most scenarios. The proposed method is tested on two complex datasets acquired by an Alpha3D mobile laser scanning system from the urban area of Shanghai, China. Experimental results show that the road boundaries and driving free space can be accurately and efficiently extracted, which also demonstrates the superiority of the proposed method.

Solidarity’s reach

Solidarity has a key role to play in the allocation of responsibility for refugee protection, as is implied by Article 80 TFEU. Yet, EU law fails to provide a definition and a clear indication of what it entails, especially as for its external reach. Against this background, this article embarks on a theoretical/practical investigation of the normative bases of ‘EU solidarity’. Building on a cosmopolitan vision, it unpacks the multi-polar/multi-functional nature of the concept, as a founding value and constitutional (meta-)principle of EU law. In such a guise, it will posit that solidarity gives rise to an (autonomous) primary law duty of responsibility sharing/good faith cooperation that requires ‘fairness’ and ‘respect for fundamental rights’, as a uniform/all-pervading structural command generally applicable across policy fields. So configured, solidarity governs intra/extra-EU relations (based on the principle of coherence). The institutional, material, and procedural aspects of solidarity are thus explored to distil its horizontal, vertical, and systemic facets. Combined, they arguably produce a triple duty of conduct, loyalty, and result that permeates EU integration as a whole, calling into question the self-serving approach currently guiding the Common European Asylum System’s (CEAS) ‘external dimension’, as exemplified by the EU-Turkey ‘deal’.

Selective-Area Growth of Vertical InGaAs Nanowires on Ge for Transistor Applications

1. Introduction Hybridized integration of III-V compound semiconductors and Ge is expected as a building block for high-performance and low-power III-V/Ge hybrid integrated circuits due to their prospects for high-mobility channel materials of the field effect transistors (FETs). Among III-V compound semiconductors, InGaAs is especially promising channel materials because of its high electron mobility. Furthermore, we can expect good heterointerfaces at InGaAs/Ge when the composition of In in InGaAs is about 70%, thus FETs based on InGaAs channel are expected to outperform their InAs counterpart. However, there are serious issues to integrate III-V materials with Ge, such as mismatches in lattice constant, polarity, and carrier mobility. Selective-area growth of InGaAs nanowires (NWs) would solve these issues because NW-footprint suppress a formation of misfit dislocation due to lattice mismatch. Also, vertical architecture using the NW can shrink their occupied area compared to conventional integrated circuits. Here we report direct integration of vertical InGaAs NWs on Ge substrate by selective-area MOVPE. 2. Experimental procedure The growth process of NWs started with the preparation of Ge(111) substrates partially masked with SiN for selective-area growth. After a 22nm-thick SiN film was deposited on Ge(111) substrates by plasma enhanced chemical vapor deposition, mask opening was defined by electron-beam lithography, and wet chemical etching. The source precursors for MOVPE growth were trimethylgallium (TMGa) and trimethylindium (TMIn) and arsine (AsH3). To form (111)B polarity on non-polar Ge(111) surfaces, following procedures were taken[1,2]. After the removal of native oxide on Ge surfaces by thermal cleaning in a hydrogen atmosphere, AsH3 was supplied for the replacement of outermost Ge with As. Then, InGaAs layers were grown, firstly by flow-rate modulated epitaxy (FME), that is, by supplying TMIn/TMGa, and AsH3 alternately with hydrogen intervals, followed by conventional MOVPE growth. The growth temperature was 670°Cand composition of TMIn in group III precursors were 63% in vapor. 3. Result and discussion When AsH3 treatment was performed at 400°C, at which it was successful for InAs[2], only part of the InGaAs NWs grew vertically on Ge. On the other hand, AsH3treatment at 670°C greatly improved the vertical alignment, indicating that (111)B polarity was successfully formed on the Ge(111) and growth direction of InGaAs nanowires was controlled into the vertical <111> direction. Optimization of the NW growth was possible by controlling AsH3 partial pressure [AsH3]. At high [AsH3], the InGaAs had a tendency to grow laterally rather than vertically, and some of the grown InGaAs exhibited short, thick, and/or hillock-like shape and unclear vertical facets. However, the percentage of NWs with vertical facets was increased under low [AsH3] because of the suppression of lateral over growth.To further enhance the yield of NW growth, we optimized number of cycles in the FME. The reduction in the FME cycles markedly increased the yield of vertical NWs, over 90%. This suggests that FME layer thinner than SiN-mask is important to suppresses lateral over growth. We analyzed InGaAs NW with 150nm in diameter and 700nm in height by energy dispersive x-ray (EDX) line profile and transmission electron microscope (TEM). EDX line-profile exhibited that the In-composition of InGaAs NW was about 80% which was larger than that of TMIn in the vapor phase and almost constant throughout the NW expect for its bottom. This suggests that the surface diffusion length of In atom is longer than that of Ga atom, thus In incorporation is enhanced in the NW growth. TEM showed that InGaAs NWs had no threading dislocations due to polarity mismatch. Instead, periodic misfit dislocations were observed at the InGaAs/Ge heterointerface. The period of misfit dislocation was 8.95nm, which was longer than the calculated value (4.37nm) based on their lattice mismatch(5.3%). This clearly indicate that the nanometer-scale footprint of NWs allows lateral deformation and limitations originating from lattice mismatch are less important than in the planer structures. 4. Summary We accomplished the growth of vertical InGaAs NWs on Ge(111) substrate along the <111>B direction by using selective-area MOVPE. We found that the percentage of NWs with clear vertical facets was improved by the optimization of the AsH3 treatment temperature, number of FME cycles, and partical pressure of AsH3. We also showed the composition of InGaAs NWs and analysis of InGaAs/Ge heterointerface. Further reduction of mask opening and NW diameter is expected to realize dislocation-free interfaces. 5. Reference [1]K. Tomioka et al., Nano Lett. 8, 3478 (2008). [2]K. Tomioka et al., Nano Lett. 15, 7253 (2015).

Measurement and analysis of internal loss and injection efficiency for continuous-wave blue semipolar (202¯1¯) III-nitride laser diodes with chemically assisted ion beam etched facets

Continuous-wave blue semipolar (202¯1¯) III-nitride laser diodes were fabricated with highly vertical, smooth, and uniform mirror facets produced by chemically assisted ion beam etching. Uniform mirror facets are a requirement for accurate experimental determination of internal laser parameters, including internal loss and injection efficiency, which were determined to be 9 cm−1 and 73%, respectively, using the cavity length dependent method. The cavity length of the uncoated devices was varied from 900 μm to 1800 μm, with threshold current densities ranging from 3 kA/cm2 to 9 kA/cm2 and threshold voltages ranging from 5.5 V to 7 V. The experimentally determined internal loss was found to be in good agreement with a calculated value of 9.5 cm−1 using a 1D mode solver. The loss in each layer was calculated and in light of the analysis several modifications to the laser design are proposed.

Cranial anatomy of Yinlong downsi (Ornithischia: Ceratopsia) from the Upper Jurassic Shishugou Formation of Xinjiang, China

ABSTRACTYinlong downsi, from the Upper Jurassic Shishugou Formation, Xinjiang, northwestern China, is the oldest known ceratopsian dinosaur. Here we provide a detailed description of the skull and mandible based on the holotype, three partial skulls, and disarticulated materials from several other specimens. Yinlong can be diagnosed by six autapomorphies: a distinct fossa along the midline of the frontals; a slit-like carotid canal bordered by laminae; premaxillary teeth with a vertical wear facet and a basal shelf; a deep sulcus on the ventral surface of the quadratojugal; large oval nodules concentrated on the lateral surface of the jugal; and a squamosal with an expanded dorsal surface and a long, constricted quadrate process. A detailed comparison with other basal ceratopsians suggests that Yinlong downsi may belong within Chaoyangsauridae. Yinlong also shares many derived characters both with Psittacosaurus and neoceratopsians, suggesting that character evolution in early ceratopsians is complex. Additionally, a caniniform premaxillary tooth is present in one small specimen (IVPP V18636), which may suggest sexual dimorphism or individual variation.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Han, F.-L., C. A. Forster, J. M. Clark, and X. Xu. 2015. Cranial anatomy of Yinlong downsi (Ornithischia: Ceratopsia) from the Upper Jurassic Shishugou Formation of Xinjiang, China. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1029579.

Asymmetric MSM sub-bandgap all-silicon photodetector with low dark current

Design, fabrication, and characterization of an asymmetric metal-semiconductor-metal photodetector, based on internal photoemission effect and integrated into a silicon-on-insulator waveguide, are reported. For this photodetector, a responsivity of 4.5 mA/W has been measured at 1550 nm, making it suitable for power monitoring applications. Because the absorbing metal is deposited strictly around the vertical output facet of the waveguide, a very small contact area of about 3 µm2 is obtained and a transit-time-limited bandwidth of about 1 GHz is demonstrated. Taking advantage of this small area and electrode asymmetry, a significant reduction in the dark current (2.2 nA at -21 V) is achieved. Interestingly, applying reverse voltage, the photodetector is able to tune its cut-off wavelength, extending its range of application into the MID infrared regime.

Comparison of Polished and Dry Etched Semipolar $(11\bar{2}2)$ III-Nitride Laser Facets

We compare facet morphology, device characteristics, and far field patterns (FFPs) for semipolar (1122) laser diodes fabricated with mechanically polished and dry etched mirror facets. Facets formed by Cl2-based dry etching produced inclined and heavily striated facets. Mechanically polished facets, in contrast, provided vertical and smooth facets (rms roughness=5.2 nm). The threshold currents of polished facet devices were on average ~ 100 and ~ 200 mA lower than etched facet devices (2 × 1200 μm2 and 4 × 1200 μm2 dimension devices, respectively). FFPs from etched facets were also shown to be obscured due to substrate reflections.