Advanced ceramic components: Materials, fabrication, and applications

The role of spontaneous and piezoelectric polarization in III-V nitride heterostructure devices is discussed. Problems as well as opportunities in incorporating polarization in abrupt and graded heterojunctions composed of binary, ternary, and quaternary nitrides are outlined.

Polarization-Engineering in III-V Nitride Heterostructures: New Opportunities For Device Design

The intrinsic electric field that exists in certain classes of materials plays a key role in many fields of electronics. Researchers reveal and correct a shortcoming in the way that the electric polarization has been modeled in a technologically important class of these materials.

https://link.aps.org/pdf/10.1103/PhysRevX.6.021038

Correct implementation of polarization constants in wurtzite materials and impact on III-nitrides

The role of spontaneous and piezoelectric polarization in III–V nitride heterostructure devices is discussed. Problems as well as opportunities in incorporating polarization in abrupt and graded heterojunctions composed of binary, ternary, and quaternary nitrides are outlined.

Polarization-engineering in group III-nitride heterostructures: New opportunities for device design

Depletion-mode high-electron mobility transistors (HEMTs) based on a quaternary barrier In0.13Al0.83Ga0.04 N/AlN/GaN heterostructure on SiC substrate were fabricated. The 66-nm-long gate device shows a dc drain current density of 2.1 A/mm, a peak extrinsic transconductance of 548 mS/mm, and a record current gain cutoff frequency fT of 220 GHz for quaternary barrier GaN-based HEMTs, which is also among the highest fT for all GaN-based HEMTs. The large Lg ·fT product of 14.5 GHz ·μm with a gate-length-to-barrier-thickness aspect ratio of 5.8 indicates a high effective electron velocity of 0.9 ×107 cm/s, attributed to a high electron Hall mobility (1790 cm2/V ·s at an ns of 1.8 ×1013-2)-the highest reported in GaN-channel HEMTs with In-containing barriers. An intrinsic electron velocity of 1.7 ×107 cm/s, extracted from conventional Moll delay-time analysis, is comparable to that reported in the state-of-art AlGaN/GaN HEMTs.

/pdf/220-ghz-quaternary-barrier-inalgan-aln-gan-hemts-34pqkrew4j.pdf

220-GHz Quaternary Barrier InAlGaN/AlN/GaN HEMTs

GaN-based high electron mobility transistors (HEMTs) with a nearly strain-free high-Al-content quaternary barrier and electron mobilities up to 1590 cm2/Vs have been grown on 4H-SiC using molecular beam epitaxy (MBE). The processed devices with 150-nm gate length exhibit a high dc performance with a maximum current density of 2.3 A/mm and an extrinsic transconductance up to 675 mS/mm that is among the highest values reported until now for any III-N transistor. We further present, to our knowledge, the first power measurements at 10 GHz of MBE-grown GaN HEMTs with nearly lattice-matched InAlGaN barrier achieving 47% power-added efficiency at 10 V and an output power density of 5.6 W/mm at 30-V bias.

GaN-Based Submicrometer HEMTs With Lattice-Matched InAlGaN Barrier Grown by MBE

Quaternary InAlGaN semiconductors with AlN mole fractions between 40% and 81% and respective InN contents of 7% and 19% including InAlN as a ternary border case have been grown by plasma-assisted molecular beam epitaxy. The electron mobility in InAlGaN-based heterostructures increases with Ga concentration in the barrier up to 1460 cm2/V s at a sheet electron density of 1.9×1013 cm−2. An advanced spacer comprising an AlN/GaN/AlN triple-layer sequence is inserted between the GaN-buffer and the InAlGaN-barrier. Transistors with thin quaternary barrier show a large current density of 2.3 A/mm and an excellent transconductance of 675 mS/mm.

Compositional variation of nearly lattice-matched InAlGaN alloys for high electron mobility transistors

Structural and compositional homogeneity of InAlN epitaxial layers nearly lattice-matched to GaN

A complete structural and compositional study was carried out for a series of GaN-based lattice-matched HEMT structures. As barrier materials pseudomorphic to GaN, both ternary InAlN and quaternary InAlGaN were investigated. Growths were performed using molecular beam epitaxy on GaN/sapphire or GaN/SiC templates. An abrupt triple-layer AlN/GaN/AlN nanothin spacer at the interface is crucial to improve the structural and electrical properties of the heterostructures. In all cases, this resulted in single-crystalline and single-phase barrier layers.

Improved Structural and Chemical Properties of Nearly Lattice-Matched Ternary and Quaternary Barriers for GaN-Based HEMTs

We present the current status of our technology for GaN-based HEMTs and MMICs as well as results ranging from the L-band up to the W-band. Epitaxial growth is carried out on 4H-SiC(0001) substrates by both MOCVD and MBE. Processing is done using standard III–V equipment including both frontside and backside processing. For L-band power bars we arrive at output powers, efficiencies and gains beyond 100 W, 60% and 17 dB, all measured under cw conditions at 50 V drain bias. The X-band MMICs are characterized by a high efficiency above 40% for two-stage amplifiers. Towards mm-wave applications we have fabricated HEMTs with transit frequencies above 100 GHz and W-band MMICs delivering 0.5 W/mm at 94 GHz with 7% PAE. First quaternary InAlGaN barriers show promising results for this new materials system. Reliability tests return a very good long-term stability of our devices even at an elevated channel temperature of 200 °C with an extrapolated lifetime of 5 × 105. Initial space capability tests including total ion dose radiation insensitivity, radiation displacement damage, hydrogen poisoning and single event effect are successfully passed.

T. Lim

Papers

GaN-Based Submicrometer HEMTs With Lattice-Matched InAlGaN Barrier Grown by MBE

Compositional variation of nearly lattice-matched InAlGaN alloys for high electron mobility transistors

Structural and compositional homogeneity of InAlN epitaxial layers nearly lattice-matched to GaN

Improved Structural and Chemical Properties of Nearly Lattice-Matched Ternary and Quaternary Barriers for GaN-Based HEMTs

GaN‐based high‐frequency devices and circuits: A Fraunhofer perspective