Low noise high performance 50nm T-gate metamorphic HEMT with cut-off frequency f_T of 440 GHz for millimeterwave imaging receivers applications

The 50 nm m-HEMT exhibits extremely high f<sub>T</sub>, of 440GHz, low F<sub>min</sub> of 0.7 dB, associated gain of 13 dB at 26 GHz with an exceptionally high Id of 200 mA/mm and gm of 950 ms/mm at low noise biased point

50-nm self-aligned and 'standard' T-gate InP pHEMT comparison: the influence of parasitics on performance at the 50-nm node

Continued research into the development of III-V high-electron mobility transistors (HEMTs), specifically the minimization of the device gate length, has yielded the fastest performance reported for any three terminal devices to date. In addition, more recent research has begun to focus on reducing the parasitic device elements such as access resistance and gate fringing capacitance, which become crucial for short gate length device performance maximization. Adopting a self-aligned T-gate architecture is one method used to reduce parasitic device access resistance, but at the cost of increasing parasitic gate fringing capacitances. As the device gate length is then reduced, the benefits of the self-aligned gate process come into question, as at these ultrashort-gate dimensions, the magnitude of the static fringing capacitances will have a greater impact on performance. To better understand the influence of these issues on the dc and RF performance of short gate length InP pHEMTs, the authors present a comparison between In0.7Ga0.3As channel 50-nm self-aligned and "standard" T-gate devices. Figures of merit for these devices include transconductance greater than 1.9 S/mm, drive current in the range 1.4 A/mm, and fT up to 490 GHz. Simulation of the parasitic capacitances associated with the self-aligned gate structure then leads a discussion concerning the realistic benefits of incorporating the self-aligned gate process into a sub-50-nm HEMT syste

50-nm T-gate metamorphic GaAs HEMTs with f_T of 440 GHz and noise figure of 0.7 dB at 26 GHz

GaAs-based transistors with the highest f/sub T/ and lowest noise figure reported to date are presented in this letter. A 50-nm T-gate In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As metamorphic high-electron mobility transistors (mHEMTs) on a GaAs substrate show f/sub T/ of 440 GHz, f/sub max/ of 400 GHz, a minimum noise figure of 0.7 dB and an associated gain of 13 dB at 26 GHz, the latter at a drain current of 185 mA/mm and g/sub m/ of 950 mS/mm. In addition, a noise figure of below 1.2 dB with 10.5 dB or higher associated gain at 26 GHz was demonstrated for drain currents in the range 40 to 470 mA/mm at a drain bias of 0.8 V. These devices are ideal for low noise and medium power applications at millimeter-wave frequencies

50 nm GaAs mHEMTs and MMICs for ultra-low power distributed sensor network applications

We report well-scaled 50 nm GaAs metamorphic HEMTs (mHEMTs) with DC power consumption in the range 1-150 ΜW/Μ demonstrating f<sub>T</sub> of 30-400 GHz. These metrics enable the realisation of ultra-low power (<500 ΜW) radio transceivers for autonomous distributed sensor network applications

Gate recess engineering of pseudomorphic In0.30GaAs/GaAs HEMTs

The authors report how the performance of 0.12 μm GaAs pHEMTs is improved by controlling both the gate recess width, using selective dry etching, and the gate position in the source drain gap, using electron beam lithography. pHEMTs with a transconductance of 600 mS/mm, off state breakdown voltages >2 V, fτ of 120 GHz, f max of 180 GHz and MAG of 13.5 dB at 60 GHz are reported

Very high performance 50 nm T-gate III-V HEMTs enabled by robust nanofabrication technologies

In this paper, we review a range of nanofabrication techniques which enable the realization of uniform, high yield, high performance 50 nm T-gate III-V high electron mobility transistors (HEMTs). These technologies have been applied in the fabrication of a range of lattice matched and pseudomorphic InP HEMTs and GaAs metamorphic HEMTs with functional yields in excess of 95%, threshold voltage uniformity of 5 mV, DC transconductance of up to 1600 mS/mm and f/sub T/ of up to 480 GHz. These technologies and device demonstrators are key to enabling a wide range of millimeter-wave imaging and sensing applications beyond 100 GHz, particularly where array-based multi-channel solutions are required

Self-aligned 0.12mm T-gate In.53Ga.47As/In.52Al.48As HEMT Technology Utilising a Non Annealed Ohmic Contact Strategy

An InGaAs/InAlAs based HEMT structure, lattice matched to an InP substrate, is presented in which drive current and transconductance has been optimized through a double-delta doping strategy. Together with an increase in channel carrier density, this allows the use of a non-annealed ohmic contact process. HEMT devices with 120 nm standard and self-aligned T-gates were fabricated using the non-annealed ohmic process. At DC, self-aligned and standard devices exhibited transconductances of up to 1480 and 1100 mS/mm respectively, while both demonstrated current densities in the range 800 mA/mm. At RF, a cutoff frequency f/sub T/ of 190 GHz was extracted for the self-aligned device. The DC characteristics of the standard devices were then calibrated and modelled using a compound semiconductor Monte Carlo device simulator. MC simulations provide insight into transport within the channel and illustrate benefits over a single delta doped structure

Histories of language learning and teaching in Europe

The articles in this special issue consider the history of learning and teaching languages within particular European countries or regions, including Britain. The papers, by leading scholars in the field, provide accessible, state-of-the-art overviews which cover similar facets of history, enabling comparisons to be usefully drawn and interconnections identified

Hegemonic gender in Japanese as a foreign language education: Australian perspectives

This chapter contests the current practice of Japanese language teaching which perpetuates and reproduces gender stereotyping and gendered language norms. It is the first of its kind which examines this question from both learner's and teacher's perspectives

Preliminary measurements of turbulence and environmental parameters in a sub-tropical estuary of Eastern Australia

In natural systems, mixing is driven by turbulence, but current knowledge is very limited in estuarine zones where predictions of contaminant dispersion are often inaccurate. A series of detailed field studies was conducted in a small subtropical creek in eastern Australia. Hydrodynamic, physio-chemical and ecological measurements were conducted simultaneously to assess the complexity of the estuarine zone and the interactions between turbulence and environment. The measurements were typically performed at high frequency over a tidal cycle. The results provide an original data set to complement long-term monitoring and the basis for a more detailed study of mixing in sub-tropical systems. Unlike many long-term observations, velocity and water quality scalars were measured herein with sufficient spatial and temporal resolutions to determine quantities of interest in the study of turbulence, while ecological indicators were sampled systematically and simultaneously. In particular the results yielded contrasted outcomes, and the finding impacts on the selection process for key water quality indicators