Gallium nitride (GaN) is a compound semiconductor that has tremendous potential to facilitate economic growth in a semiconductor industry that is silicon-based and currently faced with diminishing returns of performance versus cost of investment. At a material level, its high electric field strength and electron mobility have already shown tremendous potential for high frequency communications and photonic applications. Advances in growth on commercially viable large area substrates are now at the point where power conversion applications of GaN are at the cusp of commercialisation. The future for building on the work described here in ways driven by specific challenges emerging from entirely new markets and applications is very exciting. This collection of GaN technology developments is therefore not itself a road map but a valuable collection of global state-of-the-art GaN research that will inform the next phase of the technology as market driven requirements evolve. First generation production devices are igniting large new markets and applications that can only be achieved using the advantages of higher speed, low specific resistivity and low saturation switching transistors. Major investments are being made by industrial companies in a wide variety of markets exploring the use of the technology in new circuit topologies, packaging solutions and system architectures that are required to achieve and optimise the system advantages offered by GaN transistors. It is this momentum that will drive priorities for the next stages of device research gathered here.

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Room-temperature generation of terahertz radiation in nanometer gate length InAlAs∕InGaAs and AlGaN∕GaN high-mobility transistors is reported. A well-defined source-drain voltage threshold for the emission exists, which depends on the gate bias. Spectral analysis of the emitted radiation is presented. The highest emission power emitted from a single device reached 0.1μW.

Objectives:To report the clinical, biological, imaging features, and the clinical course of a French cohort of patients with glial fibrillar acidic protein (GFAP) autoantibodies.Methods:We retrospectively included all patients tested positive for GFAP antibodies in the cerebrospinal fluid, by immunohistochemistry and confirmed by cell-based assay using cells expressing human GFAPα, since 2017, from two French referral centers.Results:We identified 46 patients with GFAP antibodies. Median age at onset was 43 years, and 65% were men. Infectious prodromal symptoms were found in 82%. Other auto-immune diseases were found in 22% of patients, and coexisting neural autoantibodies in 11%. Tumors were present in 24%, and T cell dysfunction in 23%. The most frequent presentation was subacute meningoencephalitis (85%) with cerebellar dysfunction in 57% of cases. Other clinical presentation included myelitis (30%), visual (35%) and peripheral nervous system involvement (24%). MRI showed perivascular radial enhancement in 32%, periventricular T2 hyperintensity in 41%, brainstem involvement in 31%, leptomeningeal enhancement in 26%, and reversible splenial lesions in 4 cases. 33/40 patients had a monophasic course, associated to a good outcome at last follow-up (Rankin Score≤2: 89%), despite a severe clinical presentation. Adult and pediatric features are similar. Thirty-two patients were treated with immunotherapy. 11/22 patients showed negative conversion of GFAP antibodies.Interpretation:GFAP auto-immunity is mainly associated with acute/subacute meningoencephalomyelitis with prodromal symptoms, for which tumors and T cell dysfunction are frequent triggers. The majority of patients followed a monophasic course with a good outcome.