Photoassisted tunneling from free-standing GaAs thin films into metallic surfaces

The tunnel photocurrent between a gold surface and a free-standing semiconducting thin film excited from the rear by above bandgap light has been measured as a function of applied bias, tunnel distance and excitation light power. The results are compared with the predictions of a model which includes the bias dependence of the tunnel barrier height and the bias-induced decrease of surface recombination velocity. It is found that i) the tunnel photocurrent from the conduction band dominates that from surface states. ii) At large tunnel distance the exponential bias dependence of the current is explained by that of the tunnel barrier height, while at small distance the change of surface recombination velocity is dominant

Properties of contactless and contacted charging in MEMS capacitive switches

The dielectric charging in MEMS capacitive switches is a complex effect. The high electric field during pull-down causes intrinsic free charge migration and dipole orientation as well as charge injection. The macroscopic dipole moment of the first two mechanisms is opposite to the one arising from charge injection. This causes partial compensation hence mitigates the overall charging and increases the device lifetime. The charging due to intrinsic free charge migration and dipole orientation can be monitored under contactless electric field application in the pull-up state. The paper investigates the characteristics of contactless charging and compares them with the ones of contacted charging. The characteristics of the discharging process that follows each charging procedure are also presented

Engineered arrays of NV color centers in diamond based on implantation of CN- molecules through nanoapertures

We report a versatile method to engineer arrays of nitrogen-vacancy (NV) color centers in dia- mond at the nanoscale. The defects were produced in parallel by ion implantation through 80 nm diameter apertures patterned using electron beam lithography in a PMMA layer deposited on a diamond surface. The implantation was performed with CN- molecules which increased the NV defect formation yield. This method could enable the realization of a solid-state coupled-spin array and could be used for positioning an optically active NV center on a photonic microstructure.Comment: 12 pages, 3 figure

InP based lasers and optical amplifiers with wire-/dot-like active regions

Long wavelength lasers and semiconductor optical amplifiers based on InAs quantum wire-/dot-like active regions were developed on InP substrates dedicated to cover the extended telecommunication wavelength range between 1.4 and 1.65 mu m. In a brief overview different technological approaches will be discussed, while in the main part the current status and recent results of quantum-dash lasers are reported. This includes topics like dash formation and material growth, device performance of lasers and optical amplifiers, static and dynamic properties and fundamental material and device modelin

Lasers à boîtes quantiques sur InP à 1,55 mumum présentant en fonctionnement continu une puissance élevée, un très faible bruit et une longue durée de vie

Nous avons étudié des lasers à boîtes quantiques ayant permis d'obtenir une puissance optique élevée de 50 mW par facette, un très faible bruit d'intensité relatif de $-162\,{\rm dB/Hz}$ sur un large spectre ainsi que 7000 heures de vieillissement accéléré sans défaut ni dégradation

Simulations of radical and ion fluxes on wafer in a Cl<SUB>2</SUB>/Ar ICP discharge : Confrontation with GaAs and GaN etch experiments

International audienceA two-dimensional fluid model is used to study an industrial Ar/Cl2 inductively coupled plasma discharge designed to etch III-V samples. The effect of rf power, gas pressure, and chlorine content on the fluxes of reactive species reaching the wafer is numerically investigated. To understand how the etch process is influenced by the discharge conditions, simulation results are confronted with GaAs and GaN etch experiments performed in the same reactor geometry. When the source power is increased, the measured etch rate increase is consistent with the Cl radical and ion fluxes increase shown in the simulation, as well as the ion energy decrease due to the constant value of the wafer-holder power. Increasing the gas pressure results in a moderate increase in the etch rate due to the lower magnitude, lower mean energy, and anisotropy of the ion flux at high pressure. When the chlorine content is increased, the total ion flux decreases while Cl and Cl2 neutral fluxes increase significantly. A good correlation is obtained between calculated fluxes and etch characteristics, analyzed with scanning electron microscope images of etch profiles

Electrical properties of nanostructured SiN films for MEMS capacitive switches

The electrical properties of gold nanorods nanostructured silicon nitride films are comprehensively investigated with the aid of metal-insulator-metal capacitors and RF MEMS capacitive switches. Different nanorod diameters and densities were grown on the bottom electrode and with orientation normal to dielectric film surface. A simple physical model, which does not take the effect of electric field fringing into account, was developed to describe both the DC and low frequency electrical properties. It has been shown that the nanorods distribution and dimensions determine the electrical properties as well as the dielectric charging phenomena of the nanostructured films. Finally, in MEMS switches it has been shown that the nanorods presence does not affect the capacitance variance nor the RF characteristics of the device. © 2016 IOP Publishing Ltd

Effect of substrates and underlayer on CNT synthesis by plasma enhanced CVD

Due to their unique thermal, electronic and mechanical properties, carbon nanotubes (CNTs) have aroused various attentions of many researchers. Among all the techniques to fabricate CNTs, plasma enhanced chemical vapor deposition (PECVD) has been extensively developed as one growth technique to produce vertically-aligned carbon nanotubes (VACNTs). Though CNTs show a trend to be integrated into nanoelectromechanical system (NEMS), CNT growth still remains a mysterious technology. This paper attempts to reveal the effects of substrates and underlayers to CNT synthesis. We tried five different substrates by substituting intrinsic Si with high resistivity ones and by increasing the thickness of SiO2 insulativity layer. And also, we demonstrated an innovative way of adjusting CNT density by changing the thickness of Cu underlayer. \ua9 2013 Shanghai University and Springer-Verlag Berlin Heidelberg

Properties of contactless and contacted charging in MEMS capacitive switches

The dielectric charging in MEMS capacitive switches is a complex effect. The high electric field during pull-down causes intrinsic free charge migration and dipole orientation as well as charge injection. The macroscopic dipole moment of the first two mechanisms is opposite to the one arising from charge injection. This causes partial compensation hence mitigates the overall charging and increases the device lifetime. The charging due to intrinsic free charge migration and dipole orientation can be monitored under contactless electric field application in the pull-up state. The paper investigates the characteristics of contactless charging and compares them with the ones of contacted charging. The characteristics of the discharging process that follows each charging procedure are also presented. © 2013 Elsevier Ltd. All rights reserved