Gallium nitride (GaN) is a wide bandgap semiconductor material and the most popular after silicon in industry. The prime movers behind this trend are LEDs, microwave, more recently, power electronics. New areas of research also include spintronics nanoribbon transistors, which leverage some unique properties GaN. GaN has electron mobility comparable with silicon, but that three times larger, making it an excellent candidate for high-power applications high-temperature operation. ability to...

We report on the growth and properties of GaN films grown Si(111) substrates by molecular beam epitaxy using ammonia. The layers show that our procedure is very efficient in order to overcome difficulties encountered during nitrides silicon substrates: first, no nitridation substrate observed at interface between AlN buffer layer surface; second, there Si autodoping coming from resistive undoped are obtained; and, also, strain balance engineering allows one grow thick epilayers (up 3 μm)...

It is known that the near-field spectrum of local density states electromagnetic field above a SiC/air interface displays an intense narrow peak due to presence surface polariton. has been recently shown this wave can be strongly coupled with sheet plasmon graphene in graphene-SiC heterosystems. Here, we explore interplay between these two phenomena and demonstrate systems presents peaks whose position depends dramatically both on distance chemical potential graphene. This paves way towards...

Due to its large piezoelectric and spontaneous polarization coefficients combined with the possibility of being grown lattice-matched GaN, wide bandgap ScAlN is becoming a promising material in III-nitride semiconductor technology. In this work, for first time, growth has been performed by molecular beam epitaxy ammonia source as nitrogen precursor. High electron mobility transistor heterostructures 26 nm thick Sc0.15Al0.85N barrier have on GaN-on-sapphire substrates. The effect temperature,...

The integration of two-dimensional MoS2 with GaN recently attracted significant interest for future electronic/optoelectronic applications. However, the reported studies have been mainly carried out using heteroepitaxial templates on sapphire substrates, whereas growth low-dislocation-density bulk can be strategic realization "truly" vertical devices. In this paper, we report ultrathin films, mostly composed by single-layers (1L), onto homoepitaxial n--GaN n+ substrates sulfurization a...

The characteristics of different GaN transistor devices characterized at elevated temperatures for power applications are compared in this paper. High temperature metal-oxide-semiconductor field-effect transistors (MOSFETs) and high electron mobility (HEMTs) reported. For MOSFETs, the transconductance current (gm) increases with temperature, while HEMTs is reduced. Their specific on resistance (Ron) follows same trend. Specific contact resistivity (ρc) to implanted Si N+ also diminishes T,...

The vertical bulk (drain-bulk) current (Idb) properties of analogous AlGaN/GaN hetero-structures molecular beam epitaxially grown on silicon, sapphire, and free-standing GaN (FS-GaN) have been evaluated in this paper. experimental Idb (25–300 °C) well reproduced with physical models based a combination Poole-Frenkel (trap assisted) hopping (resistive) conduction mechanisms. thermal activation energies (Ea), the (soft or destructive) breakdown voltage (VB), effect inverting drain-bulk...

This letter reports on the demonstration of microwave power performance at 40 GHz AlGaN/GaN high-electron mobility transistor grown silicon (111) substrate by molecular beam epitaxy. A maximum dc current density 1.1 A· mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and a peak extrinsic transconductance 374 mS · are obtained for 75-nm gate length device. At VDS = 25 V, continuous-wave output 2.7 W is achieved associated with 12.5%...

High power electronics using wide bandgap materials are maturing rapidly, and significant market growth is expected in a near future. Ultra materials, which have an even larger than GaN (3.4 eV), represent attractive choice of to further push the performance limits devices. In this work, we report on fabrication AlN/AlGaN/AlN high-electron mobility transistors (HEMTs) 50% Al-content AlGaN channel, has much wider commonly used channel. The structure was grown by metalorganic chemical vapor...

Abstract Ultrawide bandgap (UWBG) semiconductors offer new possibilities to develop power electronics. High voltage operation for the off‐state as well high temperature stability of devices in on‐state are required. More than AlGaN/GaN heterostructures, AlGaN/AlGaN heterostructures promising candidates meet these criteria. Furthermore, possibility choose Al molar fraction AlGaN paves way more tunable heterostructures. In this study, electronic transport properties channel grown on silicon...

In this work, ammonia source molecular beam epitaxy is explored as an alternative technique to grow ScAlN/GaN high electron mobility transistor heterostructures on a silicon substrate with thin buffer layers. The effect of ScAlN barrier thickness investigated. A maximum drain current superior 1 mm −1 has been fabricated despite the ohmic contacts having resistance around ohm.mm, and functional transistors barriers 10 nm have demonstrated.

Abstract ScAlN is a promising barrier material for next generation RF high electron mobility transistors, outperforming AlGaN thanks higher 2-dimensional gas (2DEG) density and thinner with lower lattice mismatch GaN. A sub-10 nm ScAlN/GaN heterostructure, grown by ammonia-source molecular beam epitaxy on Si(111), processed into transistors. The 2DEG 1.6x10 13 cm -2 μ ∼ 621 2 /V.s. 75-nm gate length transistor exhibits drain current of 1.35 A/mm, transconductance ~284 mS/mm, gain cutoff...

An In/sub 0.3/Al/sub 0.7/As/In/sub 0.3/Ga/sub 0.7/As metamorphic power high electron mobility transistor (HEMT) grown on GaAs has been developed. This structure with 30% indium content presents several advantages over P-HEMT and LM-HEMT InP. A 0.15-μm gate length device a single /spl delta/ doping exhibits state-of-the-art current gain cut-off frequency F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> value of 125 GHz at V/sub ds/=1.5...

A fully integrated electromechanical resonator is described that based on high mobility piezoelectric semiconductors for actuation and detection of nanoscale motion. We employ the two-dimensional electron gas present at an AlGaN/GaN interface properties this heterostructure to demonstrate a resonant high-electron-mobility transistor enabling strain variation. In device, we take advantage polarization field divergence originated by mechanical flexural modes generating doping. This enables...

This letter reports the first millimeter-wave power demonstration of AlGaN/GaN high-electron-mobility transistors grown on a (110) silicon substrate. Owing to an AlN/AlGaN stress-mitigating stack and in spite twofold surface symmetry Si (110), it is possible obtain crack-free GaN layers for fabrication devices with high performance. The device exhibits maximum dc drain current density 1.55 A/mm at <i xmlns:mml="http://www.w3.org/1998/Math/MathML"...

As GaN technology continues to gain popularity, it is necessary control the ohmic contact properties and improve device consistency across whole wafer. In this paper, we use a range of submicron characterization tools understand conduction mechanisms through AlGaN/GaN contact. Our results suggest that there direct path for electron flow between two dimensional gas pad. The estimated area these highly conductive pillars around 5% total area.

Group III nitride semiconductors (III-N), including GaN, AlN, InN, and their alloys, are currently the materials of choice for many applications in optoelectronics (light-emitting diodes, laser diodes), high-power high-frequency transistors. Due to its attractive electrical, optical, mechanical, thermal properties, graphene (Gr) integration with III-N technology has been considered last few years, order address some major issues which still limit performances GaN-based devices. To date, most...

The electronic properties of the graphene (Gr) Schottky junction with an Al0.22Ga0.78N/GaN heterostructure on silicon have been investigated, both by experiment and use ab initio DFT calculations. A peculiarly high n-type doping (1.1 × 1013 cm–2), observed for Gr in contact AlGaN, was explained combined effect Fermi level pinning AlGaN surface states charge transfer. Spatially uniform current injection across Gr/AlGaN/GaN heterojunction revealed nanoscale resolution conductive atomic force...

This work is dedicated to the study of growth by ammonia source molecular beam epitaxy AlxGa1−xN/GaN high electron mobility transistors on (111) oriented silicon substrates. The effect conditions structural and electrical properties heterostructures was investigated. It shown that even a slight variation in temperature thick GaN buffer AlN/GaN stress mitigating layers has drastic influence these via counterintuitive dislocation density. Both situ curvature measurements ex transmission...

The growth of AlGaN/GaN-based heterostructure on Si(110) substrates by molecular beam epitaxy using ammonia as the nitrogen precursor is reported. structural, optical, and electrical properties such are assessed quite similar to ones obtained Si(111). A 2-D electron gas formed at Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> Ga xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> N/GaN interface with a sheet carrier density 9.6...

Abstract In this paper, we report on the growth of thick gallium nitride (GaN) layers 4‐in. and 6‐in., (111)‐orientated silicon substrates by metalorganic vapor phase epitaxy. Up to 4 µm continuous GaN have been obtained inserting both SiN AlN interlayers into structure. With dislocation densities about 1‐2×10 9 cm ‐2 GaN(002) (302) X‐ray rocking curve full widths at half maximum 420 1360 arcsec for 374 810 respectively, final layer exhibits excellent crystalline properties (© 2011 WILEY‐VCH...

We report an interplay between magnetism and charge transport in the ferromagnetic semiconductor GdN, pointing to formation of magnetic polarons centred on nitrogen vacancies. The scenario goes some way resolving a long-standing disagreement measured predicted Curie temperature GdN. It further constitutes extension concepts that relate closely behaviour semiconductors generally, EuO particular.

We report the growth by molecular beam epitaxy of highly resistive GdN, using intentional doping with magnesium. Mg-doped GdN layers resistivities 103 Ω cm and carrier concentrations 1016 cm−3 are obtained for films Mg up to 5 × 1019 atoms/cm3. X-ray diffraction rocking curves indicate that have crystalline quality very similar undoped films, showing did not affect structural properties films. A decrease Curie temperature decreasing electron density is observed, supporting a recently...