The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
A complete description of physical models for fabricated asymmetric spacer tunnel layer (ASPAT) diodes is reported in this paper. A novel In0.53Ga0.47As/AlAs design is presented and compared to the conventional GaAs/AlAs material system. For both material schemes, physical models were developed based on experimental measurements. Simulated dc characteristics of the devices are given for both planar-...
The electrical characterization of two asymmetric spacer layer tunnel diode samples (denoted XMBE#326 and XMBE#304) with mesa size of 16 μm2 have been undertaken to fully extract their extrinsic and intrinsic components. All measured and modelled data are in excellent agreements. Second Subharmonic mixers working at 35 GHz local oscillator signal were designed using the two samples. The minimum conversion...
Modeling and theoretically analyzing of a novel K-band reflection based amplifier was performed utilizing the unique negative differential resistance (NDR) feature of an InGaAs/AlAs RTD. A 2.4 μm2 mesa area device was fabricated and measured and on-wafer probe S-parameter measurements up to 40 GHz were carried out. Verification of the diode's equivalent circuit was experimentally validated and then...
The work presented here reports on studies of an Asymmetric Spacer Layer Tunnel (ASPAT) Diode device characteristics exploiting in-house fabricated 4×4 μm2 GaAs/AlAs and In0.53Ga0.47As/AlAs mesa diodes, grown by the molecular beam epitaxy (MBE) technique. In this study, a successfully developed numerical model, which is capable of reproducing the strong nonlinear current-voltage characteristics and...
Physical and electromagnetic modelling of double barriers InGaAs/AlAs resonant tunneling diode has been carried out using 9 μm2 mesa devices with a peak current density of 1.2 mA/μm2 integrated with a coplanar waveguide resonator. A 100 GHz oscillator was realized and achieved an output power of 100 μW through exploiting the negative differential resistance feature of the diode. Validation of the...
This work explores the applicability of Resonant Tunnelling Diodes as active elements in two different amplifier configurations in the range 25 GHz–35 GHz, with a view of implementing scaled versions at W-band and beyond, as frontend narrow-band low-noise amplifiers. On-wafer S-parameter measurements are used to represent devices in simulation software for increased fidelity. Initial results are promising,...
We report the enhancements on pHEMT epilayers to suite the high speed applications for IoT. Presented here are the DC and RF comparisons between XMBE #109 as the baseline of high speed pHEMT and VMBE #2100 as the enhanced epitaxial layer. The Hall data from Van der Pauw measurement shows higher sheet carrier concentration is observed on the improved epitaxial layer devices. The DC comparisons between...
We report a comprehensive etching study on the gate recess step for the fabrication of the novel high speed pHEMT devices. The experiments focused on the elimination of “hump” structure as a result of an incomplete etching process at the InGaAs cap layer. In this work, two types of test samples were used, namely bulk InGaAs and epitaxial structure together with an etch stop layer. The result showed...
Linear modelling of novel InGaAs/InAlAs/InP pHEMT for low noise applications is substantial to the future transistors that will operate in high speed and low noise conditions. The novel pHEMT is constructed by sandwiching two different materials together with different lattice constants, for instance InGaAs and InAlAs in order to form a heterojunction in between. However, InP is only utilised to be...
HEMT is a GaAs based field effect transistor that retains higher cutoff frequency compared to silicon based transistors. Alternatively, pHEMT enhance the performance of the HEMT in term of leakage, current conduction and the cutoff frequency of the device. The heterostructure of pHEMT improve the performance two-dimension electron gas (2DEG) in the channel layer. With these, pHEMT is believed could...
Using a novel interatomic force field, called MMP, we study the morphology of Graphene layers under a variety of strain conditions. We report that strain induced ripples possess the “right” kind of elastic deformation that is necessary in order to produce appreciable bandgap opening, which we calculate using Tight Binding, even for low enough strain that can be accessed through realistic means. At...
The work reported here proposes a new Asymmetric Spacer Layer Tunnel (ASPAT) Diode structure. The most interesting feature found from this study is the dual functions capability of the proposed device. In order to expand the device functionality, the new ASPAT has been designed with a thin potential barrier of AlAs sandwiched between double quantum wells of In18Ga.82As. The work focuses on experimental...
A GaAs/AlAs Asymmetric spacer layer Tunnel diode (ASPAT) with very thin (10ML) layer of AlAs have been successfully grown by solid source molecular beam epitaxy (SSMBE). The Current-voltage (IV) characteristics of these ASPAT diodes were measured for both different emitter geometries and over the temperature range of 77 to 398K. A comparison was made between an in-house fabricated Schottky barrier...
In the past decade ZnO nanowires have been the key enabling material for demonstrating novel electronics components in the field of piezotronics and in the first realization of a nanogenerator. What are the materials that will be crucial in demonstrating even more novel devices in future years? We propose the use of both core shell nanowires and graphene as key enablers of new functionalities.
This work presents a physical modelling for an in-house fabricated submicron InGaAs/AlAs double barrier Resonant Tunnelling diode (RTD). The modelling is developed in ATLAS SILVACO to extend the study of advanced III-V quantum devices. The Negative Differential Resistance (NDR) current and the peak-to-valley current ratio (PVCR) are simulated and validated with measurement data. The effects of structural...
This paper presents the characterisation of several solar cell devices using a single layer of anti-reflective coating (ARC). Several devices, consisting of InAs/GaAs quantum dots cylindrical diodes, were fabricated and characterised. The main difference between the used materials is the inter-dot doping profile. The J-V characteristic for the devices has been obtained under 1 sun showing an increasing...
Quantum-dot (QD) materials have shown great promise for THz photoconductive devices. The generation of THz radiation relies on the excitation of highly-mobile carriers with sub-picosecond lifetimes. The band structure of QD materials grown for such THz applications leads to a multitude of energy bands/levels [1], onto which carriers can be excited. Here we show for the first time that the lifetime...
Photoconductive devices for THz time-domain spectroscopy systems should ideally be based on materials with short carrier lifetimes, high breakdown voltages, low dark currents, and high carrier mobilities. One of the most widely used materials for such devices is low-temperature-grown (LTG) GaAs, which in its as-grown state is relatively conductive, and as such, must be annealed in order to increase...
Fifty years after tunnelling through semiconductor heterojunctions was originally investigated, the present authors are the first to demonstrate the required reproducibility, in wafer, between wafers in a given growth run, and from run to run, of the electrical properties required for manufacturing a microwave and millimetre-wave detector based on electron tunnelling through a thin semiconductor tunnel...
A simple geometric SPICE model has been developed to evaluate the effects of sidewall charge related current and depletion on the current-voltage characteristics of nanoscale resonant tunneling diodes (RTDs) and Si nanowires. The model confirms that sidewall current is the limiting mechanism for high performance nanoscale RTDs. The model can be developed to fully study the little understood parasitic...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.