InGaAsP Research Articles

Phosphorus-Controlled Nanoepitaxy of Asymmetric GaAs–InP Core–Shell Bent Nanowires: Implications for Bottom-Up Nanowire Transistors and Sensors

Phosphorus-Controlled Nanoepitaxy of Asymmetric GaAs–InP Core–Shell Bent Nanowires: Implications for Bottom-Up Nanowire Transistors and Sensors

Opto-electronic bias of a superconducting nanowire single photon detector using a cryogenic photodiode

Superconducting Nanowire Single Photon Detectors (SNSPDs) have become an integral part of quantum optics in recent years because of their high performance in single photon detection. We present a method to replace the electrical input by supplying the required bias current via the photocurrent of a photodiode situated on the cold stage of the cryostat. Light is guided to the bias photodiode through an optical fiber, which enables a lower thermal conduction and galvanic isolation between room temperature and the cold stage. We show that an off-the-shelf InGaAs–InP photodiode exhibits a responsivity of at least 0.55 A/W at 0.8 K. Using this device to bias an SNSPD, we characterize the count rate dependent on the optical power incident on the photodiode. This configuration of the SNSPD and photodiode shows an expected plateau in the single photon count rate with an optical bias power on the photodiode above 6.8 µW. Furthermore, we compare the same detector under both optical and electrical bias, and show there is no significant changes in performance. This has the advantage of avoiding an electrical input cable, which reduces the latent heat load by a factor of 100 and, in principle, allows for low loss RF current supply at the cold stage.

Two-year outcomes following the adjunctive use of InGaAsP and Er,Cr:YSGG lasers in nonsurgical periodontal therapy in patients with stages III and IV periodontitis.

To evaluate the clinical outcomes 2 years after the adjunctive use of an InGaAsP diode and Er,Cr:YSGG laser for nonsurgical treatment of severe periodontitis. Forty-two patients (45.31 ± 9.78 years old, n = 22 females, n = 23 smokers) with stage III or IV grade B periodontitis were randomly treated either with laser (InGaAsP + Er,Cr:YSGG) adjunctive to subgingival debridement (test group, n = 21) or with subgingival debridement alone (control group, n = 21). Subjects in the test group received a second laser treatment in residual sites 2 months after the initial laser therapy. At baseline, and at 12 and 24 months after therapy, periodontal clinical parameters were evaluated. The primary outcome variable was the number of residual deep sites at 12 months (probing depth [PD] ≥ 6 mm). One and two years after nonsurgical periodontal treatment, both groups yielded statistically significant clinical improvements. The adjunctive use of InGaAsP and Er,Cr:YSGG laser to mechanical debridement resulted in statistically significantly higher clinical (PD, clinical attachment level, bleeding on probing, number of sites with PD ≥ 5 mm, PD ≥ 6 mm, PD ≥ 7 mm) improvements (P < .05) compared to subgingival debridement alone both at 12 and 24 months after therapy. In patients with stage III or IV grade B periodontitis, InGaAsP and Er,Cr:YSGG used adjunctively to subgingival debridement may additionally improve the clinical outcomes compared to mechanical debridement alone over a period of 24 months.

Bending of GaAs–InP Core–Shell Nanowires by Asymmetric Shell Deposition: Implications for Sensors

Bending of GaAs–InP Core–Shell Nanowires by Asymmetric Shell Deposition: Implications for Sensors

Theoretical explanation of scanning tunneling spectrum of cleaved (110) surface of InGaAs

The cross-sectional (110) surface of In&lt;sub&gt;0.53&lt;/sub&gt;Ga&lt;sub&gt;0.47&lt;/sub&gt;As/InP hetero-structure grown by molecular beam epitaxy on an InP (001) substrate is characterized by the cross-sectional scanning tunneling microscopy (XSTM). The cleaved (110) surface across the interface between the In&lt;sub&gt;0.53&lt;/sub&gt;Ga&lt;sub&gt;0.47&lt;/sub&gt;As layer and InP layer is atomically flat but displays slight different image contrast between the two neighbor regions. The scanning tunneling spectroscopy (STS) is used to measure the current/voltage (&lt;i&gt;I-V&lt;/i&gt;) spectra. The &lt;i&gt;I-V&lt;/i&gt; data of the InGaAs surface and InP (110) surface show the different characteristics. The voltage range of zero-current plateau (apparent band gap) in the &lt;i&gt;I-V&lt;/i&gt; spectrum of InP displays the values close to its energy band gaps whereas the plateau ranges in the spectra of In&lt;sub&gt;0.53&lt;/sub&gt;Ga&lt;sub&gt;0.47&lt;/sub&gt;As are by contrast generally 50% larger than the energy band gap of In&lt;sub&gt;0.53&lt;/sub&gt;Ga&lt;sub&gt;0.47&lt;/sub&gt;As. The above phenomenon implies the different physical pictures on the tunneling of two surfaces. In the case of InP, the flat band model is feasible since the band edge states existing in the InP (110) surface can prevent the surface from being affected by the tip –induced band bending (TIBB) effect. In contrast, the TIBB effect must be taken into account to explain the &lt;i&gt;I-V&lt;/i&gt; spectra of the In&lt;sub&gt;0.53&lt;/sub&gt;Ga&lt;sub&gt;0.47&lt;/sub&gt;As (110) surface. A statistical analysis of the &lt;i&gt;I-V&lt;/i&gt; data of In&lt;sub&gt;0.53&lt;/sub&gt;Ga&lt;sub&gt;0.47&lt;/sub&gt;As reveals that the width of current plateau in the &lt;i&gt;I-V&lt;/i&gt; spectrum is generally between 1.05 eV and 1.20 eV and the current onset points (turn-points) with the plateau for the different spectra are slightly different from each other. We are able to explain quantitatively the above features based on the three-dimensional TIBB model given by Feenstra (&lt;ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://doi.org/10.1116/1.1606466"&gt;2003 &lt;i&gt;J.&lt;/i&gt; &lt;i&gt;Vac. Sci. Technol. B&lt;/i&gt; &lt;b&gt;21&lt;/b&gt; 2080&lt;/ext-link&gt;). Our calculation reveals that the parameter of density of surface states (DOSS) is a sensitive parameter responsible for the &lt;i&gt;I-V&lt;/i&gt; features mentioned above. According to an appropriate assignment of the value of DOSS, which is generally taken in the scope of (0.8–3.0) × 10&lt;sup&gt;12&lt;/sup&gt; (cm&lt;sup&gt;2&lt;/sup&gt;·eV)&lt;sup&gt;–1&lt;/sup&gt;, we well predict both the width and the onset points of the current-plateau. Moreover, the model also reproduces the line-shapes of the &lt;i&gt;I-V&lt;/i&gt; spectra measured on In&lt;sub&gt;0.53&lt;/sub&gt;Ga&lt;sub&gt;0.47&lt;/sub&gt;As.

Modeling Temperature-Dependent Avalanche Characteristics of InP

Avalanche photodiodes (APDs), and single photon avalanche diodes (SPADs), with InP avalanche regions and InGaAs absorption regions, are used for detecting weak infrared light at ∼1.55 μm wavelength. These devices are often cooled to below room temperature during operation yet both validated simulation models and impact ionization coefficients that accurately describe the avalanche characteristics of InP are lacking in the temperature range of interest (200 K to room temperature). In this article we present an accessible, validated temperature dependent simulation model for InP APDs/SPADs. The model is capable of simulating avalanche gain, excess noise, breakdown voltage, and impulse current at 150–300 K. Temperature dependent ionization coefficients in InP, which may be used with other APD/SPAD simulation models, are also presented. The data reported in this article is available from the ORDA digital repository (DOI: 10.15131/shef.data.c.4373006).

Low‐cost InP–InGaAs PIN–HBT‐based OEIC for up to 20 Gb/s optical communication systems

A detailed study of the performance analysis of a low-cost PIN/heterojunction bipolar transistor (HBT) opto-electronic integated circuit (OEIC) is described. Measured f T and f max of 54 and 57 GHz for 10 × 10 μm 2 HBTs were achieved for such a large emitter size. The base and collector regions of the transistor were utilised to form a PIN photodiode which has a dc responsivity and quantum efficiency of 0.5 A/W and 0.45, respectively, without antireflection coating at a wavelength of 1.55 μm. For both active devices, a model was realised taking all parasitic and physical-based impacts into account, for example, equivalent circuit of the pads surrounding the devices and transit delay time across the collector depletion region. The simulation results of the discrete passive and active elements showed good agreement with experimental measurements. The OEIC module was implemented in Keysight-advanced design system software with a three-stage preamplifier which has a transimpedance gain of 40 dB Ω and a -3 dB bandwidth of 18 GHz. This corresponds to a transimpedance-gain product of 1.8 THz. A series peaking inductor technique was used in the design, contributing to an enhancement in the opto-electrical bandwidth of >60%. The optical/electrical response offers a bandwidth of ~15 GHz, adequate for up to 20 Gb/s data rate operation.

Vertical InGaAs Nanowire Array Photodiodes on Si

We demonstrated vertical InGaAs nanowire (NW) array photodiodes on Si that were optically responsive to visible light (635 nm) and near-infrared light (∼1.55 μm). The vertical NWs were directly grown on Si by selective-area growth. Implementation of a heavily Sn-doped contact layer in the InGaAs NWs improved the diode characteristic because of a lower series resistance, and as a result, a photoresponsivity of 0.25 A/W was obtained at 635 nm, which was twice that before the improvement. Moreover, the photocurrent density of InGaAs–InP core–shell NWs was about 20-fold higher under illumination with light in the 1.55 μm wavelength band as a result of suppression of surface recombination. These findings are expected to be useful for NW-based photovoltaic applications for optical interconnection and Si platforms.

Monolithic integration of a InP AWG and InGaAs photodiodes on InP platform

We demonstrate a monolithic integration of a photodiode array and a 13 channels arrayed waveguide grating (AWG) grown on InP substrate with a shallow trench structure between the AWG top cladding layer and the photodiode p-doped layer. A smooth epitaxial structure interface is obtained by nonselective regrowth to make the two epitaxial structure compatible and fabrication easy. Three-dimensional finite-difference time-domain(FDTD) solutions are used in the optical simulations. The highest simulation quantum efficiency can achieve 82%. The fabricated PD with a trench structure presents a responsivity of 0.68A/W. The integrated device can achieve a total capacity of more than 200Gb/s.

A fully reconfigurable photonic integrated signal processor

Photonic signal processing has been considered a solution to overcome the inherent electronic speed limitations. Over the past few years, an impressive range of photonic integrated signal processors have been proposed, but they usually offer limited reconfigurability, a feature highly needed for the implementation of large-scale general-purpose photonic signal processors. Here, we report and experimentally demonstrate a fully reconfigurable photonic integrated signal processor based on an InP–InGaAsP material system. The proposed photonic signal processor is capable of performing reconfigurable signal processing functions including temporal integration, temporal differentiation and Hilbert transformation. The reconfigurability is achieved by controlling the injection currents to the active components of the signal processor. Our demonstration suggests great potential for chip-scale fully programmable all-optical signal processing. Scientists experimentally demonstrate a fully configurable photonic integrated signal processor based on an InP–InGaAs material system by controlling the injection currents to the active components.

Effects of buffer layer and back-surface field on MBE-grown InGaAsP/InGaAs solar cells

Solid-state molecular beam epitaxy (MBE)-grown InGaAsP/InGaAs dual-junction solar cells on InP substrates are reported. An efficiency of 10.6% under 1-sun AM1.5 global light intensity is realized for the dual-junction solar cell, while the efficiencies of 16.4 and 12.3% are reached for the top InGaAsP and bottom InGaAs cells, respectively. The effects of the buffer layer and back-surface field on the performance of solar cells are discussed. High device performance is achieved in the case of a low concentration of oxygen and weak recombination when InGaAs buffers and InP back-surface field layers are used, respectively.

Electron mobility in ultra-thin InGaAs channels: Impact of surface orientation and different gate oxide materials

Electron mobility is investigated in sub-20nm-thick InGaAs channels, sandwiched between different gate oxides (SiO2, Al2O3, HfO2) and InP as substrate, using physics-based numerical modeling. Effects of body thickness downscaling to 2nm, different gate oxides, and surface orientation [(100) and (111)] are examined by including all electron valleys and all relevant scattering mechanisms. We report that ultra-thin (111) Al2O3–InGaAs–InP devices offer greater electron mobility than (100) devices even in the extremely-thin channels. Furthermore, ultra-thin (100) InGaAs devices outperform SOI in terms of electron mobility for body thicknesses above ∼4nm, while (111) InGaAs channels are superior to SOI for all body thickness values above ∼3nm. The study of different gate oxides indicates that HfO2 is the optimum gate dielectric regardless of device orientation, offering a mobility improvement of up to 124% for (111) and 149% for (100) surface orientation, when compared to the initial Al2O3–InGaAs–InP structure. The (111) orientation offers improvement over (100) device irrespective of the body thickness and gate oxide material, with the highest difference reported for SiO2, followed by Al2O3 and HfO2.

Fabrication and characterization of novel high-speed InGaAs/InP uni-traveling-carrier photodetector for high responsivity**Project supported partially by the National Natural Science Foundation of China (Grant Nos. 61274044 and 61077049), the National Basic Research Program of China (Grant No. 2010CB327600), the Program of Key International Science and Technology Cooperation Projects, China (Grant No. 2011RR000100), the 111 Project of China (Grant No. B07005), the

A top-illuminated circular mesa uni-traveling-carrier photodetector (UTC-PD) is proposed in this paper. By employing Gaussian graded doping in InGaAs absorption layer and InP depleted layer, the responsivity and high speed response characteristics of the device are optimized simultaneously. The responsivity up to 1.071 A/W (the external quantum efficiency of 86%) is obtained at 1550 nm with a 40-μm diameter device under 10-V reverse bias condition. Meanwhile, the dark current of 7.874 nA and the 3-dB bandwidth of 11 GHz are obtained with the same device at a reverse bias voltage of 3 V.

Dependence of dark current on carrier lifetime for InGaAs/InP avalanche photodiodes

Effects of carrier lifetime of all layers on the dark current have been studied for the separate-absorption-grading-charge-multiplication InGaAs/InP avalanche photodiodes (APDs). The results indicate that the remarkably increasing of the dark current at the punch-through voltage strongly depends on the carrier lifetime of InGaAs absorption layer. According to the simulation results, we can estimate the carrier lifetime of InGaAs absorption layer and InP multiplication layer to be about 100 ns and 20 ps for our fabricated device. And we can see that the dark current of APDs near the breakdown voltage is mainly dominated by the thermal generation–recombination current from the InGaAs absorption layer and trap-assisted-tunneling current from the InP multiplication layer.

Numerical analysis of InGaAs–InP multiple-quantum well laser emitting at 2 $${\upmu }$$ μ m

Multiple-quantum well InGaAs laser structures emitting at 2 $$\upmu $$ m with different barriers are modeled using commercial software that combines gain calculation with 2-D simulations of carrier transport and waveguiding. The model is calibrated using experimental results. The simulated results show a non-uniform distribution of carriers in different quantum wells with InGaAlAs barriers which affects their contribution to the gain. The carrier uniformity and a reduction in threshold current density are observed when we use an InGaAs barrier material. The quantum well number was varied from 2 to 4 in both structures and a comparison of the threshold current and its variation with temperature were investigated.

The effects of injector doping densities on lasing properties of InP-based quantum cascade lasers at 4.3 μm

Effects of the injector doping densities on lasing properties of mid-infrared InAlAs–InGaAs–InP quantum cascade lasers at 4.3μm have been studied. Lasers with different average injector doping between 1.29E17cm−3 and 2.07E17cm−3 have been grown by gas source molecular beam epitaxy (GSMBE), and their lasing characteristics were investigated. Lasers with low doped injectors (1.68E17cm−3) exhibited lower threshold current density, longer emission wavelength and lower characteristic temperature T0. The lower injector doping density decreases waveguide loss. On the other hand, the high doping of the injector increases heat transfer through phonon in QCL active region, and thus results in high characteristic temperature T0.

The experimental investigation on dark current for InGaAs–InP avalanche photodiodes

To meet the requirement of photon-starved detection, separate absorption grading charge multiplication avalanche photodiodes (SAGCM APDs) have drawn more and more attentions. In this work, we presents a detailed analysis of dark currents for planar-type SAGCM InGaAs-InP APDs with different sub-micron thicknesses of multiplication layer, considering the effect of the diffusion process, generation-recombination process and tunneling process. According to our knowledge, it is the first time clearly demonstrating that the dominant component of dark current for a SAGCM APD changes with multiplication gain from surface to volume contribution. Our finding could be beneficial to the optimization of an APD with a SAGCM structure. An optimal InGaAs-InP APD with low-voltage operation (<40V) in combination with ultra-low dark current (0.10nA@M=8) has been demonstrated.

InGaAs–InP avalanche photodiodes with dark current limited by generation-recombination

Separate absorption grading charge multiplication avalanche photodiodes (SAGCM APDs) are widely accepted in photon starved optical communication systems due to the presence of large photocurrent gain. In this work, we present a detailed analysis of dark currents of planar-type SAGCM InGaAs-InP APDs with different thicknesses of multiplication layer. The effect of the diffusion process, the generation-recombination process, the tunneling process and the multiplication process on the total leakage current is discussed. A new empirical formula has been established to predict the optimal multiplication layer thickness of SAGCM APDs with dark current limited by generation-recombination at multiplication gain of 8.

Effects of InP crystallographic slope with light-input tapered SiO x facet on InGaAsP–InGaAs–InP waveguide photodetectors

In this paper, the influence of InP crystallographic slope with light-input tapered SiO x facet of InGaAsP–InGaAs–InP waveguide photodiodes (WGPDs) on the light-injected collection efficiency and responsivity are investigated with 3-D ray-tracing simulations and manufacturing implementation. According to our calculation results of the examination of simulations and real situations, we find that the appropriate light-input tapered facet in front of the active region designed here enlarges substantially the light-coupling aperture and therefore assists the light collection of the thin absorption layer outside of its area. The thin absorption layer of WGPDs for high frequency operation with high responsivity will be achieved by InP crystallographic slope through a simple chemical etching. The InP crystallographic slope also provides higher misalignment tolerance for fiber coupling. The anisotropic etching in appropriate processes also makes the designed WGPD have a superior current–voltage characteristic.

Near-IR Optical Upconverter With Integrated Heterojunction Phototransistor and Organic Light-Emitting Diode

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this letter, we report a near-infrared (NIR) optical upconverter consisting of an integrated InGaAs–InP heterojunction phototransistor (HPT) with an organic light-emitting diode (OLED), which converts 1.5-<formula formulatype="inline"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> IR light to visible light with a built-in electrical gain. The device was fabricated through direct tandem integration of an OLED with an inorganic InGaAs–InP HPT. Incoming 1.5-<formula formulatype="inline"><tex Notation="TeX">$\mu\hbox{m}$</tex> </formula> optical radiation is absorbed by the HPT, generating an amplified photocurrent. The resultant photocurrent drives the OLED that emits at 545 nm. Upconversion is demonstrated at room temperature with a gain of 15 from the HPT and an overall external upconversion efficiency of 0.15 W/W.<?Pub _bookmark="" Command="[Quick Mark]"?> </para>