H. Maher

H. Maher
Université de Sherbrooke | UdeS · Department of Electrical and Computer Engineering

PhD

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115
Publications
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739
Citations

Publications

Publications (115)
Article
Full-text available
This paper introduces a novel technology for the monolithic integration of GaN-based vertical and lateral devices. This approach is groundbreaking as it facilitates the drive of high-power GaN vertical switching devices through lateral GaN HEMTs with minimal losses and enhanced stability. A significant challenge in this technology is ensuring elect...
Article
The forward and reverse current transport mechanisms, temperature dependence of Schottky barrier height (SBH) and ideality factor, barrier inhomogeneity analysis, and trap parameters for Schottky barrier diodes (SBDs) fabricated on 4H-SiC, GaN-on-GaN and AlGaN/GaN epitaxial substrates are reported. High SBH is identified for Ni/4H-SiC (1.31 eV) and...
Article
Full-text available
In this work, the physical and the electrical properties of vertical GaN Schottky diodes were investigated. Cathodo-luminescence (CL), micro-Raman spectroscopy, SIMS, and current-voltage (I-V) measurements were performed to better understand the effects of physical parameters, for example structural defects and doping level inhomogeneity, on the di...
Article
Full-text available
A new vertical transistor structure based on GaN nanowire is designed and optimized using the TCAD-Santaurus tool with an electrothermal model. The studied structure with quasi-1D drift region is adapted to GaN nanowires synthesized with the bottom-up approach on a highly n-doped silicon substrate. The electrical performance is studied as a functio...
Article
The paper explores the Deep Level Transient Fourier Spectroscopy (DLTFS) capabilities in characterizing electrically active traps in vertical GaN-on-GaN Schottky barrier diodes (SBDs). The capacitance-DLTFS (C-DLTFS) experiments reveal a prominent electron trap T2 at EC – 0.56 eV with a density (NT2) of 8 × 1014 cm−3 and a weak presence of another...
Article
The impact of Cubic Silicon Carbide (3C-SiC) transition layer on breakdown voltage and frequency performance of GaN high electron mobility transistors is investigated. A combination of distinct material and device characterizations techniques, including Raman spectroscopy, coplanar waveguides, electrical measurements, and Technology Computer-Aided...
Article
This paper reports comprehensive characterization of vertical GaN-on-GaN Schottky barrier diodes (SBDs) fabricated on free-standing GaN substrates. The GaN active layer properties are evaluated by atomic force microscopy (AFM), secondary-ion mass spectrometry (SIMS), micro-Raman spectroscopy, cathodoluminescence (CL), and deep-level transient Fouri...
Article
In the present study, the selective sublimation of the p-GaN cap layer of Al(Ga)N/GaN HEMTs is developed to replace the commonly used dry etching with no risk of damage in the barrier layer in order to fabricate enhanced mode transistors. Thanks to this approach, enhancement-mode transistors are fabricated with a threshold voltage between 0V and +1...
Article
Full-text available
N-doped homo-epitaxial GaN samples grown on freestanding GaN substrates have been investigated by micro-Raman spectroscopy. Quantitative analysis of the E2h and the A1(LO) modes’ behavior has been performed while intentionally increasing the carrier density using silicon doping. We noticed that as the carrier concentration increases up to 1.8 × 101...
Article
A cost-effective fabrication process is developed to improve the power performance of AlGaN/GaN High Electron Mobility Transistors (HEMTs). This process uses nitrogen ion (N⁺) implantation to form multiple parallel nanoribbons on AlGaN/GaN heterostructures, with a thin buffer layer (AlGaN/GaN NR-HEMTs). The stopping and range of ions in matter simu...
Article
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In this paper, an AIGaN/GaN metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT) device is realized. The device shows normal ON characteristics with a maximum current of 570 mA/mm at a gate-to-source voltage of 3 V, an on-state resistance of 7.3 Ω·mm and breakdown voltage of 500 V. The device has been modeled using numerical simul...
Article
We report on the fabrication of an enhancement mode p-GaN/AlN/GaN high electron mobility transistor with selective area sublimation under vacuum of the p-GaN cap layer. The GaN evaporation selectivity is demonstrated on the thin 2 nm AlN barrier layer. Furthermore, the regrowth of AlGaN is a major key to increase the maximum drain current in the tr...
Article
Fluorine ion migration in normally-off AlN/GaN HEMTs fabricated by fluorine ion plasma implantation technology is evidenced. Devices under test are co-integrated into the OMMIC commercial D006GH/D01GH MMIC process, providing fluorine-free normally-on HEMTs. Gate reverse bias step-stress experiment at a drain fixed voltage of 0 V, carried out as wel...
Article
Full-text available
In this paper is presented a Normally-OFF GaN HEMT (High Electron Mobility Transistor) device using p-doped GaN barrier layer regrown by CBE (Chemical Beam Epitaxy). The impact of the p doping on the device performance is investigated using TCAD simulator (Silvaco/Atlas). With 4E17 cm−3 p doping, a Vth of 1.5 V is achieved. Four terminal breakdowns...
Article
Full-text available
This paper proposes a new technique to engineer the Fin channel in vertical GaN FinFET toward a straight and smooth channel sidewall. Consequently, the GaN wet etching in the TMAH solution is detailed; we found that the m-GaN plane has lower surface roughness than crystallographic planes with other orientations, including the a-GaN plane. The groov...
Article
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This paper reports on the fabrication of an enhancement-mode AlGaN/GaN metal-insulator-semiconductor-high electron mobility transistor with a new barrier epi-layer design based on double Al 0.2 Ga 0.8 N barrier layers separated by a thin GaN layer. Normally-off transistors are achieved with good performances by using digital etching (DE) process fo...
Article
Full-text available
In this paper, we report on the fabrication of a normally-off Al(Ga)N/GaN high electron mobility transistor with selective area sublimation under vacuum of the p type doped GaN cap layer. This soft method makes it possible to avoid damages otherwise induced by post processing with reactive ion etching techniques. The GaN evaporation selectivity is...
Article
Full-text available
The new power GaN transistors allow to increase the operating frequency of converters to megahertz range, thanks to their low switching time that is of a few nanoseconds or less. This permits to reduce the values and the volume of the passive components, and enhance the power density of power converters. However, inductors needed for energy storage...
Article
Full-text available
Thermal and electrical properties of aluminum nitride (AlN) epilayers grown by chemical beam epitaxy (CBE) were investigated. A high growth rate of 5.9 ± 0.4 µm/h was achieved using trimethyl aluminum and ammonia as group III and V precursors, respectively, at a growth temperature below 600 °C. The thermal conductivity and breakdown field of 10 µm...
Article
The real-time knowledge of the NO, NO2 and NH3 concentration at high temperature, would allow manufacturers of automobiles to meet the upcoming stringent EURO7 anti-pollution measures for diesel engines. Knowledge of the concentration of each of these species will also enable engines to run leaner (i.e. more fuel efficient) while still meeting the...
Article
This paper details an extraction procedure to fully model the transient self-heating of transistors from a GaN HEMT technology. Frequency-resolved gate resistance thermometry (f-GRT) is used to extract the thermal impedance of HEMTs with various gate widths. A fully scalable analytical model is developed from the experimental results. In the second...
Article
Full-text available
This paper is concerned with the determination of parasitic inductance values in very fast switching power devices. To keep improving today's power converters, new technologies are studied which exhibit very low switching times. The wide band gap semi-conductors are among the key aspects of these improvements. Thanks to their internal properties, t...
Article
This paper reports on a new method to extract the intrinsic two‐port characteristics of a high‐electron‐mobility‐transistor considering the gate resistance distributed nature knowing the gate metal sheet resistance. The procedure is straightforward. It consists of de‐embedding the extrinsic parasitic elements and access resistances, measure the gat...
Article
This paper reports on the thermal impedance measurement of GaN high‐electron‐mobility‐transistors (HEMTs) using frequency‐resolved gate resistance thermometry. Corrections methods are used to enable measurement on a very broad frequency range up to the MHz range. Transposition to time‐domain is then conducted and allows, for the first time to the a...
Conference Paper
The source/drain and gate induced charge trapping within an AlGaN/GaN high electron mobility transistor is studied, under normal device operation, by excluding self-heating effects, for the first time. Through direct measurement of current transients of both source and drain terminals, a characterisation technique has been developed to: (i) analyse...
Article
This paper describes a new method to extract the operating temperature in short-gate length AlGaN/GaN High Electron Mobility Transistors (HEMTs) dedicated to RF applications. For this goal, a nickel resistive sensor is integrated into the HEMT active area close to the hot thermal spot thanks to a well-suited technological process. Operating tempera...
Article
In this paper, the development of a soft and selective method to increase the etching rate and control accurately the etched thickness of Si3N4 material is reported. This technique combines the low damage characteristics of wet etching with the anisotropy of plasma etching which is compatible with the requirements of many surface sensitive electron...
Conference Paper
Full-text available
Power electronics applied to electrical vehicle is a field where power density, cost and weight are the main factors for dimensioning a power converter. In this context, one of the trends is to increase the working frequency and use smaller components. This can be achieved with components using technologies that allow an extremely small switching t...
Article
Transistor's thermal impedance is a parameter of prime importance to predict the device peak temperature in applications of power and RF electronics featuring time-dependent dissipated power. In the context of the upcoming GaN HEMT technology, an innovative methodology is hereby detailed for the extraction of a transistor thermal dynamic behavior....
Article
Full-text available
An optimized fabrication process of ohmic contacts is proposed to reduce the source/drain access resistance (RC) and enhance DC/RF performance of AlGaN/GaN HEMTs with a high Al concentration. We show that source/drain RC can be considerably lowered by (i) optimally etching into the barrier layer using Ar+ ion beam, and by (ii) forming recessed cont...
Conference Paper
Full-text available
Gallium nitride is a wide band-gap semiconductor material that possesses unique material properties that make it a promising candidate for high-power and high-frequency applications [1]. Low contact resistance for source and drain terminals of AlGaN/GaN HEMTs is essential to achieve high device performance. To enhance confinement in the 2-dimension...
Article
In this work, we report on the fabrication of a normally-off AlGaN/GaN Metal–Oxide–Semiconductor High Electron Mobility Transistor (MOS-HEMT) using an ultra-thin Al0.45Ga0.55N barrier layer. The AlGaN barrier was thinned down to 1 nm using a digital etching process (Oxidation/Etching) and was followed by a PECVD deposition technique of a 7 nm thick...
Article
In this letter, an AlGaN/GaN MOS-HEMT was demonstrated using a 5-nm-thick SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> dielectric layer deposited by plasma enhanced chemical vapor deposition (PECVD) as a gate insulator. The fabricated device exhibits a maximum I <sub xmlns:mml="http://ww...
Article
This paper reports on a new method for the characterization of transistors transient self-heating based on gate end-to-end resistance measurement. An alternative power signal is injected to the device output (between drain and source) at constant gate-to-source voltage. The dependence of gate resistance with temperature is used to extract the therm...
Conference Paper
In this study, InAs metal-oxide-semiconductor field effect transistors (MOSFETs) ultra-thin body (UTB) were fabricated with self-aligned method. 4 nm thick Al 2 O 3 gate oxide was deposited by Atomic Layer Deposition (ALD) technique. Ni-alloyed ohmic contacts for n-type source and drain (S/D) regions were formed at low annealing temperature (250°C)...
Article
Full-text available
In this paper, we present sensitivity measurement as well as measured and calculated absorption spectra for AlGaN/GaN THz plasmonic detector made of a metallic grating in-between two ohmic contacts. Detectors with different grating patterns have been fabricated and their sensitivity, reaching 1.9 μA/W at 77 K and 0.7 μA/W at 300 K, measured with a...
Article
A focused gas beam injection is proposed for high-efficiency ammonia molecular beam epitaxial growth of III-nitride. This new injector design is based on a double, coaxial radial high-conductance geometry, which allows rotation-free growth with fast gas switching. The injection profile is characterized through a mobile ion gauge and is then compare...
Article
In this paper, we investigate a technological route for the monolithic integration of GaN high-electron-mobility transistors (HEMTs) on silicon complementary metal oxide semiconductor (CMOS) circuits. The CMOS-first approach developed in this work relies on the ammonia-source molecular beam epitaxy (ammonia-MBE) technique which operates at noticeab...
Conference Paper
Full-text available
Electric and Hybrid Vehicles mostly use Silicon-based IGBTs for driving the motor and controlling DC/DC converters in their powertrain. IGBTs transition times usually limit their switching frequencies in the 10-100 kHz range. Gallium-Nitride semiconductors have been introduced which indicate nano-second range switching times and operating temperatu...
Conference Paper
The high power density in AlGaN/GaN High Electron Mobility Transistors (HEMTs) can notably produce strong self-heating in the device. This effect leads to performance degradation and reliability concerns. Thermal performance of the device is strongly dependent on the epitaxial structure and substrate material. This work puts into perspective the th...
Conference Paper
This paper reports on the development of a thermo-electrical non-linear model for sub-100 nm gate length AlGaN/GaN High-Electron-Mobility Transistors (HEMT) grown on silicon (111) substrate by Molecular Beam Epitaxy (MBE). The presented model benefits from the innovative implementations of a sub-network taking into account access resistances freque...
Conference Paper
We investigate plasmonic THz detectors on Al-GaN/GaN hetero-structures for different configurations of the grating (symmetric or asymmetric pattern) and spatial modulation of the electron sheet density. The absorption spectra have been calculated for the different configurations and a few detectors have freshly been fabricated and the transmission...
Article
In this paper, we investigate the reduction of thermal budgets associated with the growth of GaN high electron mobility transistor (HEMT) heterostructures. The reduction of such thermal budgets is desirable for the monolithic integration of GaN-HEMT with CMOS circuits, when the latter are fabricated first. Indeed, due to the elevated temperatures r...
Article
Full-text available
Fabrication of surface acoustic wave sensors (SAW) based on aluminum nitride (AlN) thin film are reported with improved performance using titanium nitride (TiN) nucleation buffer layer as plate electrode on (100) oriented Silicon (Si) substrate. AlN and TiN thin films are deposited at low temperature by magnetron sputtering and characterized by Xra...
Article
Full-text available
Self-heating effects in AlGaN/GaN high-electron mobility transistors (HEMTs) can notably reduce electron mobility and produce reliability concerns. Electrothermal characterization and appropriate thermal management are required to address this situation. This letter presents the measurement of channel temperature ( $mathbf T_ch$ ) of GaN HEMTs in m...
Article
Full-text available
Temperature measurements in AlGaN/GaN high electron mobility transistors are required for proper device design, modeling and achieving appropriate reliability. These measurements usually require sophisticated equipment and extensive calibration. This study evaluates the feasibility of temperature measurements by integration of a Pt resistance therm...
Article
We report a 94-GHz large-signal load-pull characterization of InP/GaAsSb double heterojunction bipolar transistors. The investigated devices have an emitter area of 0.20 x 9.5 mu m(2). Biased for highest power added efficiency (PAE), an output power of 6.62 mW/mu m(2) (11 dBm), a power gain of 5.2 dB, and a PAE of 27.7% have been obtained. Biased f...
Article
Full-text available
In this letter, we present an effective GaN surface passivation process, which was developed by optimizing the surface chemical pretreatment prior to the PECVD-SiOₓ deposition. It is demonstrated that the electronic properties of the GaN/SiOₓ interface are drastically influenced by the surface preparation conditions. Among the used chemicals, we fo...
Article
L'étude présentée a pour objectif la détermination des propriétés électriques d'un échantillon par la caractérisation de lignes de transmissions coplanaires (CPW) de dimensions et de nature différentes. La structure étudiée est une structure Métal Isolant Semiconducteur (MIS) pour laquelle la partie isolante est constituée de 2 diélectriques déposé...
Conference Paper
A delay time analysis is carried out for SiN-passivated AlGaN/GaN High Electron Mobility Transistors (HEMTs) on silicon substrate featuring gate length of 90 nm. The influence of high parasitics in the access pads is considered using de-embedding procedure from the measured S parameters. From the obtained transit delay contributions, the effective...
Conference Paper
Full-text available
From the characterization of structure equivalent loss tangent under different conditions (bias and temperature) obtained through propagation constant and characteristic impedance extraction of CPW line, we propose a coherent analysis of the properties of an AlN/Si interface featured with a GaN on Si HEMT technology.
Article
Full-text available
This letter reports on AlGaN/GaN high-electron-mobility transistors (HEMTs) on high-resistive silicon substrate with a record maximum oscillation cutoff frequency F-MAX. Double-T-shaped gates are associated with an optimized technology to enable high-efficiency 2-D electron gas control while mitigating the parasitic resistances. Good results of F-M...
Article
A delay time analysis is carried out for SiN-passivated AlGaN/GaN High Electron Mobility Transistors (HEMTs) on silicon substrate featuring gate length of 90 nm. The influence of high parasitics in the access pads is considered using de-embedding procedure from the measured S parameters. From the obtained transit delay contributions, the effective...
Article
Self-aligned 0.55 x 3.5 mu m(2) emitter InP/GaAsSb/InP double heterojunction bipolar transistors demonstrating an f(t) of 310 GHz and an f(max) of 480 GHz are reported. Common-emitter current gain of 24, together with a breakdown voltage of 4.6 V, is measured. The devices were fabricated with a triple-mesa process and easily fabricated with a new b...
Article
The FP7 Research for SME project IMAGINE - a low cost, high performance monolithic passive mm-wave imager front-end is described in this paper. The main innovation areas for the project are: i) the development of a 94 GHz radiometer chipset and matching circuits suitable for monolithic integration. The chipset consists of a W-band low noise amplifi...
Conference Paper
We report on the reliability of InP/GaAsSb/InP DHBTs dedicated to very high-speed ICs applications. The devices under tests were fabricated by OMMIC [1]. Accelerated aging tests under thermal stress were previously performed on the same technology and the results are detailed in [2]. In this paper, we present the accelerated aging tests under bias...
Conference Paper
A K-band (18–26.5 GHz) single-chip reconfigurable and multi-functional RF-MEMS switched dual-LNA MMIC (optimized for lowest/highest possible noise figure/linearity) is presented. The two MEMS switched low-NF and high-linearity LNA circuit functions present 18.6 dB/9.0 dB, 2.4 dB/3.5 dB and 22 dBm/29 dBm of small-signal gain, noise figure and OIP3 a...
Conference Paper
this article summarizes the overall progress made during the last 4 project years of the FP7 EU-project MEMS-4-MMIC that focuses on the merging of innovative RF-MEMS (Micro-Electrical-Mechanical-Systems) switch designs with established MMIC-technology. The final goal is to include RF-MEMS switches into a standard commercial foundry process. Such sw...
Article
A report is presented on high transconductance Gm measured on AlGaN/GaN HEMTs with a 12.5 nm-thick AlGaN barrier layer, grown on high resistivity silicon substrate using the MOCVD growth technique. 105 nm T-gate transistors were successfully fabricated using Pt/Ti/Pt/Au Schottky contact. Maximum current density of 723 mA/mm, current gain cutoff fre...
Conference Paper
Platinum (Pt/Ti/Pt/Au) gate contact of AlGaN/GaN high electron mobility transistor (HEMT) with low gate leakage current is demonstrated. For comparison, Titanium (Ti/Al/Ti) gate devices are also fabricated using the same process flow except the gate topology which is double T-shaped gate for Ti/Al/Ti. Comparable extrinsic transconductance is obtain...
Conference Paper
This paper presents a BCB cap packaging of MEMS switches integrated with MMIC and its electrical and mechanical effects to the packaged devices have been also investigated. To prevent a possible breakage during BCB bonding process, the 100 µm-thick MMIC wafer is bonded to 680 µm-thick GaAs support that will be finally released using PMMA sacrificia...
Article
In this paper, a fully passivated InP/GaAsSb/InP DHBT on InP substrate with excellent DC and RF performance is developed. The epi-layers are grown by the MOCVD technique, with a base layer of 25nm and a collector layer of 130nm. The emitter width of the transistor is 0.35μm and the base contact is 0.3μm wide. The base and emitter contacts present a...