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Edward Wasige - IEEE Xplore Author Profile

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In this paper, we study the effect of temperature changes on the noise performance of GaN high electron mobility transistors (HEMTs) covering a wide temperature range (77 K to 400 K) and frequency range (2 GHz to 30 GHz). The measurement system consists of a temperature-controlled manual probe station and a vector network analyser (VNA) which has a built-in active source tuner and a sensitive nois...Show More
This study presents an in-depth investigation into the high-frequency capabilities of a commercial 100 nm InP high electron mobility transistor (HEMT) through small and large signal analysis. The report centres on the analysis of output power, gain, and power-added efficiency (PAE), aiming to provide an accurate and comprehensive evaluation of device performance. Initially, the DC characteristics ...Show More
In this work, normally-off, aluminium nitride (AlN)/ gallium nitride (GaN) high electron mobility transistors (HEMTs) were successfully fabricated with T-gate structures. GaN HEMTs with A1N barriers and 70 nm T-gates exhibited +0.62V of threshold voltage ($\mathrm{V}_{\mathrm{t}\mathrm{h}}$), 1.15mV/V of drain induced barrier lowering (DIBL), and $\mathrm{f}_{\mathrm{T}}$/fmax of 89/232 GHz. This ...Show More
We report experimental investigation of time refractory time on optoelectronic neuromorphic receiver circuit built with a nanoscale resonant tunnelling diode-photodetector (RTD-PD), capable to produce optically induced spiking events with nanosecond repetition rate. RTDs are voltage-controlled nano-electronic semiconductor epilayer elements that includes a double barrier quantum well structure whi...Show More
We report an optoelectronic neuromorphic synaptic link built with high-speed nanoscale resonant tunnelling diode-photodetectors (RTD-PDs), which reproduces temporal-coded spike generation and transmissions in biological neurons and synapses. The artificial optoelectronic neuron is composed of a nanoscale RTD-PD built with a double barrier quantum well (DBQW) structure for nonlinearity and excitabi...Show More
Nondestructive testing (NDT) and imaging of materials with unknown properties are important applications of terahertz technology. Different contrast-forming methods are available to obtain diverse information on the imaged region, including intensity, color, phase, and polarization. Polarimetric imaging is relatively under-investigated owing to the difficulty in its implementation with complex opt...Show More
We report on very high power resonant tunnelling diode (RTD) based monolithic microwave integrated circuit (MMIC) oscillators with 35 mW output power at 11 GHz and 10 mW at 49 GHz. The key to these high powers is the use of an epitaxial layer structure that give devices with large peak to valley voltage span ($\Delta$V) of 1.2 V and the use of large area devices to get large peak to valley current...Show More
We report a spiking artificial optoelectronic neuron based on a resonant tunnelling diode (RTD) coupled to a photodetector (receiver) and a vertical cavity surface emitting laser (VCSEL, transmitter). We experimentally realize this O/E/O system, and demonstrate optical spiking with a well-defined, adjustable excitability threshold.Show More
$A$ high-power double-barrier resonant tunnelling diode (RTD) epitaxial structure in InP technology is reported. The heterostructure exhibits moderate available current density $\Delta J\simeq 1.4\ \text{mA}/\mu \mathrm{m}^{2}$ and large voltage swing $\Delta V\simeq 1.2$ V, resulting in a maximum RF power $P_{RF,\max}\simeq 0.31\ \text{mW}/u\mathrm{m}^{2}$, and over 530 GHz bandwidth, being 25 $\...Show More
We report about an In0.53Ga0.47As/AlAs doublebarrier resonant tunnelling diode (RTD) epitaxial structure that features high-power capabilities at low-terahertz frequencies (∼ 100−300 GHz). The heterostructure was designed using a TCAD-based quantum transport simulator and experimentally investigated through the fabrication and characterisation of RTD devices. The high-frequency RF power performanc...Show More
We present an epitaxial structure simulation study of In0.53Ga0.47As/AlAs double-barrier resonant tunnelling diodes (RTD) employing Atlas TCAD quantum transport simulation software developed by SILVACO, which is based on the non-equilibrium Green’s function (NEGF) formalism. We analyse how epitaxial layers design impacts the heterostructure static current density-voltage (JV) characteristic, inclu...Show More
In this article, we demonstrate a reliable physics-based simulation approach to accurately model high-speed In0.53Ga0.47As/AlAs double-barrier resonant tunneling diodes (RTDs). It relies on the nonequilibrium Green’s function (NEGF) formalism implemented in SILVACO Atlas TCAD quantum simulation package to closely mimic the actual device physics, together with the judicious choice of the material p...Show More
This paper presents 22 Gbps wireless link over 80 cm distance by using high power J-band resonant tunnelling diode (RTD) transmitter (Tx). The RTD Tx fundamental frequency is 278 GHz with around 1 mW output power. The system energy efficiency can reach 0.1 pJ per cm distance. No frequency multiplier, power amplifier or synthesizer was employed, and fabrication process is fully compatible with low-...Show More
This paper describes the systematic approach to develop low power consumption excitable neuromorphic spike generators using nano-sized resonant tunnelling diode (RTD), including fabrication, characterization and device modelling and spike circuit simulation. The fabrication process of nano sized RTDs has been developed and devices exhibit peak currents of up to 100 μA. The energy efficiency of the...Show More
Resonant tunneling diode (RTD) technology is emerging as one of the promising semiconductor-based solid-state technologies for terahertz (THz) wireless communications. This article provides a review of the state of the art, with a focus on the THz RTD oscillator, which is the key component of RTD-based THz transmitters and coherent receivers. A brief summary on the device principle of operation, t...Show More
In this paper, we present low cost THz wireless transmission system utilizing 278GHz resonant tunneling diode (RTD) transmitter (Tx) with around ImW output power. The demonstration shows 12Gbps error free and 1080p30 (3Gbps) HD video real time transmission over 80 cm distance. These results demonstrate very promising future of RTD Tx for next generation wireless communication system.Show More
An in-plane resonant cavity-assisted coplanar waveguide (CPW) to rectangular waveguide (WG) transition is realized over an Indium Phosphide (InP) substrate with a thickness of 205 µm using a monopole radiating element. The simulated back-to-back (B2B) structure provides a bandwidth 16 GHz (288 - 304 GHz) with a return loss of 10 dB and insertion loss of 0.6 dB.Show More
In this paper, the process of designing and building of energy harvesting device to collect "free" RF ambient energy is presented. This experiment was conducted for a bachelor's degree Final Year Project at the University of Glasgow. The Power Scavenger device consists of a microstrip wideband antenna, a full wave rectifier and a capacitor as unit storage. The antenna has an omnidirectional radiat...Show More
A novel front end for high data rate point to point links at D-band (151 - 174.8 GHz) will provide up to 45 Gb/s over 1 km range. The low power signal generation is provided by a low cost Resonant Tunnelling Diode (RTD) oscillator. The RTD oscillator is connected to a Traveling Wave Tube that provides up to 10 W transmission power.Show More
Terahertz (THz) oscillators based on resonant tunneling diodes (RTDs) have relatively low output power, tens to hundreds of microwatts. The conventional designs employ submicron-sized RTDs to reduce the device self-capacitance and, as a result, realize higher oscillation frequencies. However, reducing the RTD device size leads to lower output power. In this article, we present RTD oscillators that...Show More
This paper describes a new project to realize a high data rate point to point wireless system above 150 GHz. The upper end of the D-band spectrum is used (151 -174 GHz) for full duplex transmission. The aims it to enable a full fiber on air with more than 1 km range to provide up to 45 Gb/s data rate. The system consists in a transmitter using a directly modulated Resonant Tunnelling Diode (RTD) o...Show More
This paper presents a monolithic microwave integrated circuit (MMIC) that combines two resonant tunneling diodes (RTDs) in parallel. By employing appropriate circuitry and improved device epilayer design, the oscillators generate an output power of 2 mW at 84 GHz and 1 mW at 206 GHz which are the highest power reported for RTD-based oscillators in the respective frequency bands. Also, preliminary ...Show More
This article presents a novel, on-wafer deembedding technique for the accurate small-signal equivalent circuit modeling of resonant tunneling diodes (RTDs). The approach is applicable to stabilized RTDs, and so enables the modeling of the negative differential resistance (NDR) region of the device's current-voltage (I-V) characteristics. Furthermore, a novel quasi-analytical procedure to determine...Show More
We report on high-efficiency, high-power, and low-phase-noise resonant tunneling diode (RTD) oscillators operating at around 30 GHz. By employing a bias stabilization network, which does not draw any direct current (dc), the oscillators exhibit over a tenfold improvement in the dc-to-RF conversion efficiency (of up to 14.7%) compared to conventional designs (~0.9%). The oscillators provide a high ...Show More
This brief presents AlGaN/GaN high electron mobility transistor (HEMT) devices with improved thermal and dc current-voltage (I-V) performance using a novel method of obtaining a distributed channel device, i.e., the total semiconductor area between the ohmic contacts comprise conducting and nonconducting regions. A novel oxygen (O2) plasma treatment technique is used to realize the inactive or non...Show More