Interdigitated metal–semiconductor–metal (MSM) photodetectors have received considerable attention for applications in microwave optical phoswitches. The impulse response of photoswich interdigitated fabricated metal-semiconductor- on GaAs metal non-intentional doped (NID) absorbing layer is investigated. The photodetector MSM is introduced in the microwave lines have active surfaces of 3x3 m2 and electrode spacing of 0.2, 0.3, 0.5 and 1 m.. The photocurrent response was measured after excitation and we found that the screening of the dark electric field and charge accumulation exceedingly modify the drift conditions of the photogenerated electrons and holes in active region of the MSM photoswich.

This paper reports on pin photodiode frequency response optimization based on InxGa1-xAs1-yNy quaternary lattice matched to GaAs. Two transparent layers are placed on p-side and n-side in order to manage the photodiode frequency response limitations. The lattice matching condition is calculated in order to obtain stable structure. The physical and optical parameters calculations are performed at room temperature showing the impact of nitrogen on the absorption coefficient. A stable structure, having 2 % of nitrogen and 6% of indium, allows to achieve a cutoff frequency of about 116 GHz and a capacitance of 5.21fF while the quantum efficiency is 41.59% for a depletion region thickness of about 0.55 mu m. However, in case of depletion region thickness of about 0.625 um, the cutoff frequency degrades to 98 GHz while the capacitance diminishes to 4.58fF and the quantum efficiency increases to 51.56%. In addition, a comparative study with literature results has been carried out in order to show the advantages of the proposed photodiode. This comparison affirms that the proposed photodiode based on InGaAsN lattice matched to GaAs exhibits high-speed photo-detection. This work allowed us to obtain a p-i-n photodiode with stable structure suitable for photo-detection at 1.15 mu m.

The objective of this study is to study, design, and develop a high-speed PIN photodiode based on In x Ga 1-x N/GaN alloys deposited by metal-organic chemical vapor deposition. The configuration used for the PIN photodiode is based on an absorbing layer composed of In 0.1 Ga 0.9 N multiple quantum wells. Structural, microstructural, and optical analyses have been carried out using TEM, PL, and absorption measurement. The design of PIN structures varies with an active surface ranging from 10 4 to 10 6 μm 2 . Static and dynamic characterizations have been performed to qualify the photodiode response. A photocurrent value reaching a maximum of 1.2 mA is reported for a diode of 100 x 100 μm 2 area, with an external quantum efficiency of 13%. Using the noise measurement technique, the device reveals a -3-dB cutoff frequency of 300 MHz for the same photodiode. This result clearly shows the potential of III-nitride materials for targeting high-speed optoelectronics. The future prospect is to work toward InGaN-based microphotodiodes in order to achieve optical transmission links in the UV-visible range using the same material system.

In this work, we report a comparative investigation of InxGa1-xN (SL) and InxGa1-xN/GaN (MQW) structures with an indium content equivalent to x=10%. Both structures are grown on (0001) sapphire substrates using MOCVD and MBE growth techniques. Optical properties are evaluated for samples using PL characteristics. Critical differences between the resulting epitaxy are observed. Microstructures have been assessed in terms of crystalline quality, density of dislocations and surface morphology. We have focused our study towards the fabrication of vertical PIN photodiodes. The technological process has been optimized as a function of the material structure. From the optical and electrical characteristics, this study demonstrates the benefit of InGaN/GaN MQW grown by MOCVD in comparison with MBE for high speed optoelectronic applications.

We present the experimental determination of the complex permittivity of vertically aligned single wall carbon nanotubes (SWCNTs) films grown on quartz substrates in the microwave regime from 10 MHz up to 67 GHz, with the electrical field perpendicular to the main axis of the carbon nanotubes (CNTs), based on coplanar waveguide transmission line approach together with the measurement of the microwave impedance of top metalized vertically—aligned SWCNTs grown on conductive silicon substrates up to 26 GHz. From coplanar waveguide measurements, we obtain a real part of the permittivity almost equal to unity, which is interpreted in terms of low carbon atom density (3 × 1019 at/cm3) associated with a very low imaginary part of permittivity (<10−3) in the frequency range considered due to a very small perpendicular conductivity. The microwave impedance of a vertically aligned CNTs bundle equivalent to a low resistance reveals a good conductivity (3 S/cm) parallel to the CNTs axis. From these two kinds of data, we experimentally demonstrate the tensor nature of the vertically grown CNTs bundles.

A GaAs Photonic Crystal based photoconductive switch is controlled by mode-locked fiber laser operating in the Telecom spectra, owing to efficient nonlinear interaction. The bandwidth reaches > 10 GHz owing to the strong surface recombination.

This Letter reports on new experimental high dynamic range sub-sampling performances obtained from nanoscale microwave photoconductive switches operating under a 0.8 µm wavelength pulsed illumination. Experimental results have been performed on different samples benefiting of a low temperature grown Gallium Arsenide absorbing layer on GaAs substrate, coplanar microwave electrode profile optimisation, and the use of an ultra-low noise jitter optical source delivering optical pulses of 1 to10 ps pulse width at a 2 GHz repetition frequency at 0.8 µm optical wavelength. Thanks to carrier lifetime tunability achievement from 1 to 20 ps, in association with a carrier mobility of 3900 cm²/V.s, experimental demonstrations of 54 and 45 dB signal-to-noise ratio microwave signal sampling for signals at 5,76 and 20 GHz frequency bandwidth respectively confirms submicron devices functionality as a new class of single channel photonic analogue to digital converters.

The potential of GaAs-based photonic crystals for fast all-optical switching in the telecom spectral range is exploited by controlling the surface recombination and, thereby, the carrier relaxation dynamics. The structure is entirely coated with a layer of aluminium oxide using atomic layer deposition. This results in a carrier lifetime of about 10 ps, as determined by spectrally resolved pump-probe measurements. We show that the nonlinear response of the resonator is optimized when it is excited with a few-picoseconds pulse. This dynamics is perfectly captured by our model accounting for the carrier diffusion with an impulse response function. Moreover, the suppression of photo-induced oxidation is revealed to be crucial to demonstrate all-optical operation at GHz rates with average coupled pump power of 0.5 mW (hence 100 fJ/bit). The switching window is 12 ps wide (1/e), as resolved by homodyne pump-probe measurements. The devices respond to a sequence of closely spaced pump pulses demonstrating a gating window close to 10 ps, with a contrast as high as 7 dB.

In this work, we report a comparative investigation of In x Ga 1-x N (SL) and In x Ga 1-x N/GaN (MQW) structures with an indium content equivalent to x=10%. Both structures are grown on (0001) sapphire substrates using MOCVD and MBE growth techniques. Optical properties are evaluated for samples using PL characteristics. Critical differences between the resulting epitaxy are observed. Microstructures have been assessed in terms of crystalline quality, density of dislocations and surface morphology. We have focused our study towards the fabrication of vertical PIN photodiodes. The technological process has been optimized as a function of the material structure. From the optical and electrical characteristics, this study demonstrates the benefit of InGaN/GaN MQW grown by MOCVD in comparison with MBE for high speed optoelectronic applications.

The main purpose of this paper is to show the effect of charge accumulation and screening of the electric field on the Schottky Metal-semiconductor-Metal detector response and efficiency, which result of non-uniform distribution carriers along the absorption depth, and along the line between electrodes. The MSM (PD) with an active surface of 3×3 μm 2 and electrode spacing of 0.2, 0.3, 0.5 and 1 μm has been integrated in the central strip of coplanar lines for microwave switching application. Several ways of improving the high-speed response of the MSM-PD are analyzed and discussed.

In this paper, the frequency response calculation and optimization of PIN photodiodes based on GaN/InGaN, suitable for photodetection at the wavelength of 633 nm, are presented. The calculations of the impulse as well as the frequency response are performed using the impulse method. The frequency response optimization is a result of optimizing the transport of photo-generated carriers in the absorbent layer of the photodiode, using a mixed depletion region rather than a single absorbing depletion region. Cut-off frequencies of about 82 GHz and 48 GHz have been obtained in the case of transparent layer thickness of 500 nm and 1000 nm, respectively. The aforementioned results represent a very good improvement. (C) 2015 Elsevier B.V. All rights reserved.

Atomic Layer Deposition is used to control the surface recombination of carriers in GaAs photonic crystal cavities. All-optical wavelength conversion at a GHz repetition rate is demonstrated with recovery time below 10 ps.

Photogenerated carriers in a photodiode drift in the junction before joining the circuit. We must use a quite thin depletion region so that their transit time does not penalize the microwave response of the devices. However, when the depletion region decreases the component capacity increases, which highly limits the microwave response of this latter. Replace the completely absorbent depletion region by a mixed depletion region increases the pure transit cut-off frequency for the same thickness of the depletion region. We use this property in what follows to optimize the performance of PIN photodiode based on InP/InGaAs, adapted for the photodetection at the wavelength of 1.55 μm. The obtained results show that the maximum area of photodiodes with mixed depletion regions with thin absorbent exceeds by 64% that of the photodiodes with completely absorbent depletion regions for the same bandwidth. Their maximum absorption volume exceeds by 8% that of the photodiodes with completely absorbent depletion regions for the same bandwidth. Both types of components are also compared on the abacuses when the thickness of the absorbent and the surface are imposed.

The carrier lifetime of a photonic crystal all-optical switch is optimized by controlling the surface of GaAs by Atomic Layer Deposition. We demonstrate an all optical modulation capability up to 100GHz at Telecom wavelengths, with a contrast as high as 7dB. Wavelength conversion has also been demonstrated at a repetition rate of 2.5GHz with average pump power of about 0.5mW

In this paper we present the optimization of photoswitches constituted of a coplanar line introducing interdigitated MSM photodetectors in the central strip. The reflection and the transmission coefficients are studied with the aim of highlighting the influence of different geometrical parameters on the photoswitch microwave behavior. In pursuance of improving the performances, new topologies of coplanar lines introducing tapers of linear shapes, as well as tightening of ground planes around the central strip are proposed and studied. The outcomes showed that it is possible to achieve high insulation (-52.3 dB) at the Off state. As for as the On/Off ratio is concerned, a value of 48.8 dB is reached. (C) 2014 Elsevier Ltd. All rights reserved.

In this paper we present the simulation of the planar Metal-Semiconductor-Metal photodetector (MSM-PD) of interdigitated structure based on InAlAs/GaAsSb adapted for photodetection at the wavelength 1.3 μm. We use theoretical models to plot the variations of the dark current, the photocurrent, the capacity, and the cut-off frequency of the photodetector as a function of bias voltage and the different geometrical parameters. The obtained results show a very low dark current of 30-100 pA, observed at the bias voltage of 10 V, this is mainly due to the introduction of a thin layer to increase the Schottky barrier, based on In0.52Al0.48As in the epitaxial structure of the component. The obtained photocurrent and cutoff frequencies are very appreciable, these latter exceed the value of 2 THz for a photodetector having an active surface of 1 × 1 μm2 and an interelectrode distance of 0.03 μm, and they are mainly limited by the transit time of the photo-generated carriers, given the low component capacity obtained by simulation.

In this paper we present the simulation of Metal-Semiconductor-Metal photodetector (MSM-PD) of interdigitated planar structure based on InAlAs/InGaAs adapted for photodetection at the wavelength 1.55μm. We use the theoretical models to plot the variations of the dark current, the photocurrent, the capacity, and the cut-off frequency of the photodetector as a function of bias voltage and the interelectrode distance. The obtained results show a very low dark current, mainly due to the introduction of a thin layer to increase the Schottky barrier based on In0.52Al0.48As in the epitaxial structure of component. The obtained photocurrent and cut-off frequencies are very appreciable, these latter are mainly limited by the transit time of the photo-generated carriers given the low component capacity obtained by simulation.

Photo-generated carriers in a photodiode drift in the junction before joining the circuit. We must use a quite thin depletion region so that their transit time does not penalise the microwave response of the devices. However, when the depletion region decreases the component capacity increases, which highly limits the microwave response of this latter. The solution proposed in this work is the use of a mixed depletion region instead of a completely absorbent depletion region in order to have a low transit time while maintaining a low junction capacity. The obtained results show that the photodiodes with mixed depletion regions are faster than photodiodes whose depletion region is completely absorbent for the same thickness. The pure transit cut-off frequency of optimised mixed depletion regions exceeds by 67% that of completely absorbent depletion region for the same thickness of the depletion region.

Gallium nitride (GaN) on silicon (Si) is governed by the possibility to use this family of semiconductor for novel optoelectronic devices. GaN layers are deposited by MOCVD on silicon Si (111) using AlGaN buffer layer. We have studied the microstructure quality of the films. From SEM, TEM and AFM observations, we have observed that the films exhibit a good quality: the films are highly oriented (0001) with a smooth surface morphology (roughness of 12nm). We have completely characterized the optical properties using the prism coupling technique.

We report here the experimental results on a field effect refractive index change into gallium nitride (GaN) structures. This effect is characterized through the common prism-coupling technique with the application of a vertical direct-current electric field. Surface plasmon propagation was used to increase the sensitivity of the electro-optic measurements. We have obtained a large refractive index variation for GaN epilayer, around 1.4×10−2 at 1.55μm wavelength. In order to understand the origin of the index modulation, we have conducted a scanning transmission electron microscopy analysis and discussed the influence of threading dislocations density acting as traps and thermo-optic effect. According to recent works, we observed experimentally the optical response of a non-linear electro-optic effect on GaN on Si(111) substrate and estimated a Kerr coefficient of about 2.14×10−16m2 V−2.