A. Soltani - Academia.edu (original) (raw)

Papers by A. Soltani

2013 Saudi International Electronics, Communications and Photonics Conference, 2013

In this work the effects of technological and electrical parameters of Al m Ga 1-m N/GaN High Ele... more In this work the effects of technological and electrical parameters of Al m Ga 1-m N/GaN High Electron Mobility Transistors (HEMT) on the output conductance "g d " was studied in the first part. In the second part, the effect on g d of thermal and self heating in the device was analyzed. This study was made by taking into account the effects of spontaneous and piezoelectric polarizations in the heterojunction AlGaN/GaN and the relaxation of the crystal lattice induced by the aluminum mole fraction. An analytical model for the electrons concentration "n s " in the 2DEG and the current I ds in the channel for strong inversion regime was presented. By solving the Poisson equation and Schrödinger self-consistent calculations, including the spontaneous and piezoelectric polarizations, lattice relaxation, self heating and thermal effects the current I ds was calculated. The output conductance g d according to the voltage V ds are deduced thanks to the analytical description of the calculated current I ds .

Thin Solid Films, 2005

Thin films of hexagonal boron nitride (h-BN) were grown by a plasma enhanced chemical vapour depo... more Thin films of hexagonal boron nitride (h-BN) were grown by a plasma enhanced chemical vapour deposition (PECVD) technique. The quality of the films was assessed by infrared spectroscopy, microRaman spectroscopy as a function of annealing temperature and by X-ray photoelectron spectroscopy. The films proved to be thermally stable up to 1370 K. Current-voltage measurements were performed, as a function of humidity, using metal-insulator-semiconductor and metal-insulator-metal structures. Typical resistivities were found in the range 10 13-10 14 V cm in dry air and exhibit high sensitivity against humidity. The influence of the mean orientation of the c-axis of the BN films was considered. Sawtooth voltage pulse trains were also applied. Threshold switching phenomena were observed, but only in atmosphere containing humidity. The values of the switching voltages depend strongly on the relative humidity (RH), on the characteristics of the applied sawtooth voltage pulse trains, as well as on the nature of the metallic electrode.

Advanced Engineering Materials, 2002

Proceedings of the 10th EAI International Conference on Body Area Networks, 2015

This paper presents a low-actuation-voltage micro-electromechanical system (MEMS) capacitive shun... more This paper presents a low-actuation-voltage micro-electromechanical system (MEMS) capacitive shunt switch which has a very large bandwidth (4 GHz to 24 GHz). In this work, the isolation of MEMS switch is improved by adding two short high impedance transmission lines at the beginning and end of a coplanar waveguide (CPW). Simulating the switch demonstrates that a return loss (S11) is less than-26 dB for the entire frequency band, and perfect matching at 20 GHz in upstate position. A ramp dual pulse driver is also designed for reducing the capacitive charge injection for considering the reliability of the switch. The simulation results show that the shifting of voltage due to the capacitive charge is reduced by more than 35% of the initial value. Finally, the dynamic behavior of the MEMS switch is simulated by modal analysis and using CoventorWare to calculate the natural frequencies of the switch and its mode shapes. The switching ON and OFF time are 4.48 and 2.43 µs, respectively, with an actuation voltage of less than 15 V.

Thin Solid Films, 2008

Deep level transient spectroscopy (DLTS) and photoluminescence (PL) techniques are used to study ... more Deep level transient spectroscopy (DLTS) and photoluminescence (PL) techniques are used to study the defects occurring at the interface between hexagonal Boron Nitride (hBN) films and n-type Indium Phosphide (n-InP). The BN films are deposited on InP using plasma enhanced chemical vapor deposition. The measured DLTS spectra shows four discrete peaks labelled ET1, ET2, ET3 and ET4. The results are

Semiconductor Science and Technology, 2008

... For the LYRA project (Large Yield RAdiometer) [6], several diamond photodetectors (PIN and MS... more ... For the LYRA project (Large Yield RAdiometer) [6], several diamond photodetectors (PIN and MSM detectors) were fabricated and characterized [7, 8]. LYRA is a solar VUV radiometer that will embark in 2008 onboard PROBA-2 (PRoject for On-Board Autonomy), a ...

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2013

Journal of Applied Physics, 2012

ABSTRACT Ballistic transport in double-barriers resonant tunneling diodes based on GaN is investi... more ABSTRACT Ballistic transport in double-barriers resonant tunneling diodes based on GaN is investigated in this work using the non-equilibrium Green's functions formalism. The electron density of states, the electrons concentration, and the current-voltage characteristics are calculated taking into account the internal electric field induced in the AlxGa1−xN/GaN heterostructures. The effect of the geometrical parameters on the evolution of the current resonances characteristics was analyzed qualitatively by varying GaN quantum well width, thicknesses and height of the AlxGa1−xN barriers.

IEEE Transactions on Electron Devices, 2009

A self-consistent electrothermal transport model that couples electrical and thermal transport eq... more A self-consistent electrothermal transport model that couples electrical and thermal transport equations is established and applied to AlGaN/GaN device structures grown on the following three different substrate materials: 1) SiC; 2) Si; and 3) sapphire. Both the resultant I-V characteristics and surface temperatures are compared to experimental I-V measurements and Raman spectroscopy temperature measurements. The very consistent agreement between measurements and simulations confirms the validity of the model and its numerical rendition. The results explain why the current saturation in measured I-V characteristics occurs at a much lower electric field than that for the saturation of electron drift velocity. The marked difference in saturated current levels for AlGaN/GaN structures on SiC, Si, and sapphire substrates is directly related to the different self-heating levels that resulted from the different biasing conditions and the distinctive substrate materials.

Diamond and Related Materials, 2009

ABSTRACT Metal/Insulator/Semiconductor AlGaN/GaN High Electron Mobility Transistors (MISHEMTs) on... more ABSTRACT Metal/Insulator/Semiconductor AlGaN/GaN High Electron Mobility Transistors (MISHEMTs) on sapphire substrate were fabricated with hexagonal Boron Nitride (hBN) thin film as gate dielectric. The hBN thin film, deposited by MW-PECVD, is an insulator permitting to obtain a low leakage current gate, an interface state density as low as 5 × 1011 cm− 2 eV− 1 for hBN/AlGaN interface and low roughness surface less than 0.4 nm. HBN thin film is deposited to have optical c-axis oriented weakly tilted to the perpendicular at the AlGaN barrier surface and to increase the lateral electrical resistivity. DC measurement on MISHEMT exhibits promising performance for microwave power devices associated to a good gate charge control in enhancement mode.

Applied Physics Letters, 1996

Core-level photoabsorption has been used to determine the sp2 and sp3 bonding content of nanocrys... more Core-level photoabsorption has been used to determine the sp2 and sp3 bonding content of nanocrystalline diamond thin films grown using C60 or CH4 precursors. The C(1s) absorption spectra show clear bulk diamond excitonic and sp3 features with little evidence of sp2 bonding, while the Raman spectra measured from these same films are ambiguous and indeterminate. This result can be attributed

Agronomie, 1993

Effets de NaCl et de Na 2 SO 4 sur les bilans des échanges ioniques en milieux NO-3 /NH + 4 et su... more Effets de NaCl et de Na 2 SO 4 sur les bilans des échanges ioniques en milieux NO-3 /NH + 4 et sur les coûts énergétiques de la croissance chez l'orge (Hordeum vulgare L)

Chinese Physics B, 2009

Optical absorption, reflectivity, and photoconductivity in the near-uv range (1950-3200 A) of a t... more Optical absorption, reflectivity, and photoconductivity in the near-uv range (1950-3200 A) of a thin film of hexagonal boron nitride were measured. The m»~absorption peak was observed at 6.2 eV. A sharp fall at abeet 5.8 eV was attributed to the direct band gap. The temperature dependence of the band gap was found to be less than 4 X 10 ' eV/X. Self-consistent tight-binding band-structure calculations were performed on a twe4imensiona1 hexagonal crystal model, using H~miltonian matrix elements calculated by semiempirical LCAO (linear combination of atomic orbitals) methods. The calculated value for the band gap of hexagonal SN was in reasonably good agreement with the experimental value obtained in the present work, as well as with values reported earlier from electron-energy-loss and photoelectron-emission measurements. The calculations also predicted a very small change in the band gap with temperature, in agreement with the experimental observations.

Electronics Letters, 2010

ABSTRACT In this reported work, the thermal resistance of AlGaN/GaN HEMTs processed on SopSiC com... more ABSTRACT In this reported work, the thermal resistance of AlGaN/GaN HEMTs processed on SopSiC composite substrate is determined by electrical I-V pulsed measurement. SopSiC substrate is based on an innovative structure with a thin Si single crystal layer transferred on top of a thick polycrystalline SiC wafer. For the first time, it is demonstrated that the thermal resistivity of such devices reaches 18.9 K mm/W when 7.5 W/mm power is dissipated, while 23.5 K mm/W are measured on silicon in the same conditions. This result shows the capabilities of composite substrates to compete with silicon for microwave power applications.

Journal of Magnetism …, 2009

We report the use of a magnetic instability of the spin reorientation transition type to enhance ... more We report the use of a magnetic instability of the spin reorientation transition type to enhance the magnetoelectric sensitivity in magnetostrictivepiezoelectric structures. We present the theoretical study of a clamped beam resonant actuator composed of a piezoelectric element on a ...

ABSTRACT Boron doped diamond layers have been grown on (110) single crystal diamond substrates wi... more ABSTRACT Boron doped diamond layers have been grown on (110) single crystal diamond substrates with B/C ratios up to 20 ppm in the gas phase. The surface of the diamond layers observed by scanning electron microscopy consists of (100) and (113) micro-facets. Fourier Transform Photocurrent Spectroscopy indicates substitutional boron incorporation. Electrical properties were measured using Hall effect from 150 to 1000 K. Secondary ion mass spectrometry analyses are consistent with the high incorporation of boron determined by electrical measurements. A maximum mobility of 528 cm2.V- 1.s- 1 was measured at room temperature for a charge carrier concentration of 1.1 1013 cm- 3. Finally, properties of boron doped (110) diamond layers are compared with layers on (100) and (111) orientated substrates.