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Dive into the research topics where Abdullah Al-Khalidi is active.

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Featured researches published by Abdullah Al-Khalidi.


IEEE Electron Device Letters | 2014

A Sub-Critical Barrier Thickness Normally-Off AlGaN/GaN MOS-HEMT

R. Brown; Douglas Macfarlane; Abdullah Al-Khalidi; Xu Li; G. Ternent; H. Zhou; I.G. Thayne; Edward Wasige

A new high-performance normally-off gallium nitride (GaN)-based metal-oxide-semiconductor high electron mobility transistor that employs an ultrathin subcritical 3 nm thick aluminium gallium nitride (Al0.25Ga0.75N) barrier layer and relies on an induced two-dimensional electron gas for operation is presented. Single finger devices were fabricated using 10 and 20 nm plasma-enhanced chemical vapor-deposited silicon dioxide (SiO2) as the gate dielectric. They demonstrated threshold voltages (Vth) of 3 and 2 V, and very high maximum drain currents (IDSmax) of over 450 and 650 mA/mm, at a gate voltage (VGS) of 6 V, respectively. The proposed device is seen as a building block for future power electronic devices, specifically as the driven device in the cascode configuration that employs GaN-based enhancement-mode and depletion-mode devices.


Journal of Applied Physics | 2014

Investigation of the GaN-on-GaAs interface for vertical power device applications

Janina Möreke; Michael J. Uren; S. V. Novikov; C. Thomas Foxon; Shahrzad Hosseini Vajargah; David J. Wallis; Colin J. Humphreys; Sarah J. Haigh; Abdullah Al-Khalidi; Edward Wasige; I.G. Thayne; Martin Kuball

GaN layers were grown onto (111) GaAs by molecular beam epitaxy. Minimal band offset between the conduction bands for GaN and GaAs materials has been suggested in the literature raising the possibility of using GaN-on-GaAs for vertical power device applications. I-V and C-V measurements of the GaN/GaAs heterostructures however yielded a rectifying junction, even when both sides of the junction were heavily doped with an n-type dopant. Transmission electron microscopy analysis further confirmed the challenge in creating a GaN/GaAs Ohmic interface by showing a large density of dislocations in the GaN layer and suggesting roughening of the GaN/GaAs interface due to etching of the GaAs by the nitrogen plasma, diffusion of nitrogen or melting of Ga into the GaAs substrate.


Proceedings of SPIE | 2017

Resonant tunnelling diode terahertz sources for broadband wireless communications

Edward Wasige; Khalid Alharbi; Abdullah Al-Khalidi; Jue Wang; Ata Khalid; Gil C. Rodrigues; J. M. L. Figueiredo

This paper will discuss resonant tunnelling diode (RTD) sources being developed on a European project iBROW (ibrow.project.eu) to enable short-range multi-gigabit wireless links and microwave-photonic interfaces for seamless links to the optical fibre backbone network. The practically relevant output powers are at least 10 mW at 90 GHz, 5 mW at 160 GHz and 1 mW at 300 GHz and simulation and some experimental results show that these are feasible in RTD technology. To date, 75 - 315 GHz indium phosphide (InP) based RTD oscillators with relatively high output powers in the 0.5 – 1.1 mW range have been demonstrated on the project. They are realised in various circuit topologies including those that use a single RTD device, 2 RTD devices and up to 4 RTD devices for increasingly higher output power. The oscillators are realised using only photolithography by taking advantage of the large micron-sized but broadband RTD devices. The paper will also describe properties of RTD devices as photo-detectors which makes this a unified technology that can be integrated into both ends of a wireless link, namely consumer portable devices and fibre-optic supported base-stations (since integration with laser diodes is also possible).


Third International Conference on Applications of Optics and Photonics | 2017

Resonant Tunneling Diode Oscillators for Optical Communications

Scott Watson; Weikang Zhang; Jue Wang; Abdullah Al-Khalidi; Horacio I. Cantú; J. M. L. Figueiredo; Edward Wasige; Anthony E. Kelly

The ability to use resonant tunneling diodes (RTDs) as both transmitters and receivers is an emerging topic, especially with regards to wireless communications. Successful data transmission has been achieved using electronic RTDs with carrier frequencies exceeding 0.3 THz. Specific optical-based RTDs, which act as photodetectors, have been developed by adjusting the device structure to include a light absorption layer and small optical windows on top of the device to allow direct optical access. This also allows the optical signal to directly modulate the RTD oscillation. Both types of RTD oscillators will allow for seamless integration of high frequency radio and optical fiber networks.


international conference on ultra modern telecommunications | 2017

THz electronics for data centre wireless links — The TERAPOD project

Abdullah Al-Khalidi; Khalid Alharbi; Jue Wang; Edward Wasige

This paper presents an overview of the terahertz (THz) resonant tunneling diode (RTD) technology that will be used as one of the approaches towards wireless data centres as envisioned on the eU H2020 TERAPOD project. We show an example 480 gm × 680 gm THz source chip at 300 GHz employing a 4 gm × 4 gm RTD device with 0.15 mW output power. We also show a basic laboratory wireless setup with this device in which up to 2.5 Gbps (limited by equipment) was demonstrated.


Third International Conference on Applications of Optics and Photonics | 2017

Resonant tunneling diode photodetectors for optical communications

Gil C. Rodrigues; João F. Rei; James A. M. Foot; Khalid Alharbi; Abdullah Al-Khalidi; Jue Wang; Edward Wasige; J. M. L. Figueiredo

Resonant tunneling diodes (RTDs) have been extensively studied due to their potential applications in very high speed electronics, optical communications, and terahertz generation. In this work, we report the latest results on the characterization of the resonant tunneling diode photo-detectors (RTD-PDs), incorporating InGaAlAs light sensitive layers for sensing at the telecommunication wavelength of λ = 1310 nm. We have measured responsivities up to 28.8 A/W and light induced voltage shift of 204.8 V/W for light injection powers around 0.25 mW.


Third International Conference on Applications of Optics and Photonics | 2017

Resonant tunnelling diode based high speed optoelectronic transmitters

Jue Wang; Gil C. Rodrigues; Abdullah Al-Khalidi; J. M. L. Figueiredo; Edward Wasige

Resonant tunneling diode (RTD) integration with photo detector (PD) from epi-layer design shows great potential for combining terahertz (THz) RTD electronic source with high speed optical modulation. With an optimized layer structure, the RTD-PD presented in the paper shows high stationary responsivity of 5 A/W at 1310 nm wavelength. High power microwave/mm-wave RTD-PD optoelectronic oscillators are proposed. The circuitry employs two RTD-PD devices in parallel. The oscillation frequencies range from 20-44 GHz with maximum attainable power about 1 mW at 34/37/44GHz.


2017 10th UK-Europe-China Workshop on Millimetre Waves and Terahertz Technologies (UCMMT) | 2017

Resonant tunneling diode as high speed optical/electronic transmitter

Jue Wang; Abdullah Al-Khalidi; Cui Zhang; Afesomeh Ofiare; L. Wang; Edward Wasige; J. M. L. Figueiredo

We report both electronic and opto-electronic resonant tunneling diode (RTD) oscillators with relatively high output power. Electronic RTD oscillators working at 125/156/308 GHz with around one half milliwatt output power and optoelectronic oscillators in the 30–105 GHz range with about 1 mW output power at 44 GHz have been developed. First wireless transmission experiments with a 300 GHz oscillator are also reported.


2016 IEEE 9th UK-Europe-China Workshop on Millimetre Waves and Terahertz Technologies (UCMMT) | 2016

High performance microstrip resonant tunneling diode oscillators as terahertz sources

Edward Wasige; Abdullah Al-Khalidi; Khalid Alharbi; Jue Wang

This paper prepents monolithic microwave integrated circuits (MMIC) employing large size resonant tunneling diode (RTD) with high power at high frequencies. This is achieved by proper design of the resonating inductances which are realized by shorted microstrip transmission lines with low characteristic impedances (Z0 = 10.4 Ω). Two oscillators were fabricated using photolithography. Oscillation frequencies of 312 GHz delivering 0.15 mW and 262 GHz delivering 0.19 mW were measured for oscillators employing a single 4 μm × 4 μm and 5 μm × 5 μm RTD devices, respectively.


conference on ph.d. research in microelectronics and electronics | 2015

AlN/GaN HEMT technology with in-situ SiN x passivation

Abdullah Al-Khalidi; Ata Khalid; Edward Wasige

We report on the fabrication of low resistance Ohmic contacts on AlN/GaN HEMT material terminated with in-situ SiNx. The AlN/GaN material was grown on SiC substrate using metal organic chemical vapor deposition (MOCVD), and employs a 5nm in-situ SiNx layer to reduce the cracking of the highly stressed AlN layer. A low Ohmic contact resistance of 0.4 Ω.mm was achieved, and this is one of the lowest reported values. 2×200 μm finger AlN/GaN HEMT devices exhibited a maximum drain current density, IDSS, of 700 mA/mm, which in comparison with standard AlGaN/GaN HEMT devices (on SiC) was at least 2× higher.

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Jue Wang

University of Glasgow

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R. Brown

University of Glasgow

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S. Taking

University of Glasgow

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