H. Maher

Optimized Pre-Treatment Process for MOS-GaN Devices Passivation

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 found that KOH/HCl leads to the best GaN/SiOx interface quality. MOS capacitors fabricated using this pretreatment have shown a near ideal capacitance-voltage characteristics, with a good surface potential modulation, small flatband voltage shift, low hysteresis, and no significant frequency dispersion. Using this optimized passivation process, AlGaN/GaN-based MOS-high electron mobility transistors (HEMTs) were fabricated. Electrical characterizations have shown up to four orders of magnitude lower gate leakage current and three orders of magnitude lower off-state current compared with the reference Schottky gate HEMT.

A K-band single-chip reconfigurable/multi-functional RF-MEMS switched dual-LNA MMIC

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 at 20 GHz, respectively. The in-band isolation levels of the two switched LNA paths equal 16–20 dB when the MEMS switches are switched on and off. Compared with two fixed (non-reconfigurable) LNA breakout circuits, the MEMS switched LNA circuit functions show 0.5–1.0 dB higher NF together with similar values of linearity at 15–25 GHz.

IMAGINE project - A low cost, high performance, monolithic passive mm-wave imager front-end

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 amplifier, fabricated using the commercially available OMMIC D007IH GaAs mHEMT process, and a zero bias resonant interband tunneling diode, fabricated using a patented epi-layer structure that is lattice matched to the same D007IH process; ii) the development of a 94 GHz antenna adapted for low cost manufacturing methods with performance suitable for real-time imaging; iii) the development of a low cost liquid crystal polymer PCB build-up technology with performance suitable for the integration and assembly of a 94 GHz radiometer module; iv) the assembly of technology demonstrator modules. The results achieved in these areas are presented.

480-GHz

Self-aligned 0.55×3.5 μm² 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 base isolation μ-airbridge design which, moreover, significantly reduced the base-collector capacitance C_BC.

f_{\max}

This paper reports the capability of AlGaN/GaN HEMTs on Si (111) substrates for microwave power applications above 30GHz. A current gain cut-off frequency ft=90GHz and a maximum power gain cut-off frequency fmax=135GHz are obtained for a 80nm gate-length transistor. These results, associated with low lag effects, demonstrate the capability of these transistors for high performance, cost effective, MMIC fabrication on a Si substrate for high frequency microwave power applications.

in InP/GaAsSb/InP DHBT With New Base Isolation

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 temperatures up to 200°C, with the promise of many advantages in the automotive market. Faster GaN devices will eventually lead to higher switching frequencies and lower switching losses, lower power electronic volume and weight reduction. Faster switching comes with cheaper inductors and capacitors. The silicon (Si) has reached its limits regarding the dynamic performance and conduction losses, which is why several manufacturers and researchers are working on new materials, such as gallium nitride (GaN) for new power devices development. In the paper, a comparison is made between GaN and Si in terms of cost, performance advantages and upcoming improvements. Challenges are highlighted, as driving a high-power device in nanoseconds comes with many unresolved difficulties.

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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 thermal detector (RTD) in an “un-gated” transistor and evaluating their electrical interactions. The integrated RTD presents the advantage of being independent of the device. Micro RTD showed a linear response in the calibration interval (0 to 206 °C). Measured temperature values using the micro RTD are in agreement with 3D finite element simulations at multiple bias conditions in the “un-gated” transistor. Measurements show no noticeable electrical perturbation between the device and RTD under simultaneous operation.

-Airbridge Design

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 sacrificial etching. The implemented BCB caps on the target MMIC have the height of 28 µm and the cavity of 13 µm for the housing of MEMS switches. The achieved success rate of BCB caps transfer is approximately 80 %. The BCB cap packaging effect to microstrip line has been investigated through the S-parameters measurement before and after the packaging. Also, the packaged MEMS switch shows the insertion loss of 0.7 dB, the return loss of 25 dB and the isolation of 18 dB at 30 GHz.

AlGaN/GaN HEMT on Si (111) substrate for millimeter microwave power applications

In this paper, a 200 nm n-channel inversion-type self-aligned In0.53Ga0.47As MOSFET with a Al2O3 gate oxide deposited by Atomic Layer Deposition (ALD) is demonstrated. Two ion implantation processes using silicon nitride side-wall are performed for the fabrication of the n-type source and drain regions. The 200 nm gate-length MOSFET with a gate oxide thickness of 8 nm features the transconductance of 70 mS/mm and the maximum drain current of 200 mA/mm.

Gallium Nitride Semiconductors in Power Electronics for Electric Vehicles: Advantages and Challenges

This letter 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 thermal impedance of the device in frequency domain via electrical measurement. This new method is validated on common-gate AlGaN/GaN high-electron-mobility transistors on Si substrate under different experimental conditions, which demonstrates its potential to provide complete dynamic self-heating models for power transistors.