Binary AlN/GaN high electron mobility transistors (HEMTs) were grown by plasma-assisted molecular beam epitaxy (PA-MBE) as well as metal-organic chemical vapor deposition (MOCVD) and compared with regard to their structural and electrical properties. The investigated structures differ in Al distribution and composition of the AlN barrier due to characteristic differences of the two growth methods such as growth temperature and interface sharpness. While we observe a nearly pure AlN layer and an abrupt interface for MBE growth, a graded "AlN" barrier with a significant amount of Ga is found for the MOCVD grown structures which is reflected by the electrical properties of the HEMT structures. Si-implanted ohmic contacts were formed on MBE as well as MOCVD grown structures. The activation anneal step subsequent to implantation at temperatures ~1100°C changes the observed Al profiles of MBE structures and damages the active region, whereas MOCVD samples react insensitively and thus were able to be further processed. A maximum drain current of ~1.46 mm(-1) at a gate source voltage of +3 V is observed for the processed devices. A current-gain cut-off frequency of 89 GHz and maximum oscillation frequency of 208 GHz were measured, which demonstrate an excellent small-signal performance of AlN/GaN devices with 100nm gate length

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Through implementation of the 3-D tri-gate topology, GaN-based high-electron mobility transistors (HEMTs) have been fabricated and high-frequency performances as well as the short-channel effects are investigated. The designed tri-gate transistors are highly-scaled having 100 nm of gate length, which introduces the condition of a short channel. It is demonstrated that higher sub-threshold slopes, reduced drain-induced barrier lowering and better overall off-state performances have been achieved by the nano-channel tri-gate HEMTs with an AlGaN barrier. A lattice-matched InAlGaN barrier with the help of the fin-shaped nano-channels provide improved gate control, increasing current densities, and transconductance g m . In a direct comparison, very high drain current densities (∼3.8 A/mm) and g m (∼550 mS/mm) have further been obtained by employing a pure AlN barrier.INDEX TERMS High-electron mobility transistor (HEMT), fin-shaped field-effect transistor (FinFET), Gallium nitride, short channel.

In this paper the recent use AlGaN/GaN high electron mobility transistors (HEMTs) and integrated circuits on both semi‐insulating silicon carbide (SiC) and silicon substrates for radio communication in the microwave and mm‐wave frequency range is described. AlGaN/GaN monolithically microwave integrated circuits (MMICs) are extremely useful for point‐to‐point (P2P)‐links in the backbones of the 4th and upcoming 5th generation of mobile communication networks as power amplifiers, as they provide a great amount of linear power. At the same time GaN‐based power conversion electronics has driven the advancement of the growth of AlGaN/GaN heterostructures on conductive silicon (111) substrates. This again has indirectly led to advancements in the growth capabilities of AlGaN/GaN heterostructures on highly‐resistive (HR) silicon substrates. The paper gives examples of transistors and microstrip transmission‐line‐based MMICs realized in a direct comparison of GaN on s.i. SiC and GaN on HR‐silicon. Constraints and performances for highly‐efficient MMICs are discussed up to mm‐wave frequencies beyond 100 GHz.

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This paper reports on the monolithic integration of layout-optimized Schottky diodes realized in an established 50-nm gate-length metamorphic high-electron-mobility transistor technology for use in multifunctional nonlinear circuits. The suitability of the realized Schottky diodes is demonstrated by a broadband millimeter-wave I/Q-mixer (In-phase/Quadrature) and local oscillator (LO) chain comprising two power amplifiers and a frequency tripler, fabricated on monolithic microwave integrated circuits (MMICs). Both circuits are based on an anti-parallel Schottky diode topology. The subharmonically-pumped I/Q-mixer covers an RF (radio frequency) and IF (intermediate frequency) range of at least 75 GHz to 110 GHz and 0.5 GHz to 15 GHz, respectively. The single-sideband conversion loss is between 14 dB and 16 dB across most of the entire RF and IF bands. The core of the LO chain consists of a frequency tripler (multiplier by three) and features a bias-adjustable output power with almost constant conversion efficiency and a control range of more than 8 dB. The fully-integrated LO chain MMIC matches the needs of the presented I/Q-mixer and exhibits an average output power of 16.3 dBm with a covered frequency range of 38 GHz to 60 GHz. The unwanted harmonics are suppressed by at least =25.9 dBc below the third harmonic for the entire frequency range and better than =32.1 dBc for most part of the band. Thus, the mixer and tripler MMICs demonstrate state-of-the-art performance with regards to, e.g., covered bandwidth, output power, harmonic suppression, or 1 dB compression point.

AlGaN/GaN high-electron mobility transistors (HEMTs) with varied Tri-gate topologies have been fabricated and influences of the fin-shaped nano-channels on device parasitics are examined. Through S-parameter measurements and modelling of the designed Fin-FETs, a detailed RF investigation on intrinsic device parameters is performed under different biasing schemes. Corresponding RF performances and transfer characteristics as well as the derived small-signal parameters of the measured devices are extracted by employing 3-D EM FET model analysis at 110 GHz. Comparisons between the designed fin-geometries and intrinsic device parameters have proven flatter gm, gds and fT responses, which are presented through experimental results in detail for the first time