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In this paper, a set-up based on the internal IR-laser deflection technique is described. This technique allows measurement of the temperature gradient and free-carrier concentration inside power semiconductor devices with high spatial (35 µm) and time (less than 1 µs) resolution. The internal IR-laser deflection technique consists in the measurement of deflection and absorption of an IR-laser beam passing through a biased power device. After describing the operational principle and the experimental set-up, the postprocessing methodology followed to extract the temperature gradient and free-carrier concentration is detailed. In order to show the set-up functionality, the drift region of a 600 V PT-IGBT device has been studied. These measurements are very helpful for performing reliability or thermal management studies on power semiconductor devices.

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This paper studies the overload turnoff failure in the insulated-gate bipolar transistor (IGBT) devices of power multichip modules for railway traction. After a detailed experimental analysis carried out through a dedicated test circuit, electrothermal simulations at device level are also presented. The simulation strategy has consisted in inducing a current and temperature mismatch in two IGBT cells. Results show that mismatches in the electrothermal properties of the IGBT device during transient operation can lead to uneven power dissipation, significantly enhancing the risk of failure and reducing the lifetime of the power module. Concretely, simulations qualitatively demonstrate that localized hot-spot formation due to a dynamic breakdown could lead to a second breakdown mechanism.Index Terms-Insulated-gate bipolar transistor (IGBT) power module, power inverter reliability, railway applications, semiconductor device breakdown, semiconductor device thermal factors.

Lateral n-channel enhancement-mode GaN metal-oxide-semiconductor ͑MOS͒ field-effect transistors and lateral capacitors have been fabricated on a p-type epi-GaN substrate semiconductor and electrically characterized at different temperatures. A clear positive behavior of the inversion channel mobility with temperature has been obtained. A physics-based model on the inversion charge and charge trapped in interface states characteristics has been used to investigate the temperature dependence of the inversion MOS channel mobility. The field-effect mobility increase with temperature is due to an increase in the inversion charge and a reduction in the trapped charge for a given voltage gate. Then, for larger gate bias and/or higher temperatures, surface roughness effects become relevant. The good fitting of the model with the experimental data leads us to consider that the high density of charged acceptor interface traps together with a large interface roughness modulates the channel mobility due to scattering of free carriers in the inversion layer. A closed form expression for the experimental inversion MOS channel mobility is proposed.

increased speed of analysis, reduced sample consumption, and waste production, portability, disposability as well as the potential for on-site use. [1] In the context of electrochemical devices, the integration of versatile conductive materials on chip is required for implementing electroanalytical platforms in different scenarios including (bio)chemical sensing or energy and electrocatalytic applications. Among them, carbon materials, in a variety of forms from graphite to amorphous carbon as well as carbon nanotubes or graphene, [2][3][4] have been combined with various fabrication approaches based on thick film (screen-printing) [5] or thinfilm (lithographic) [6] technologies for producing reproducible and inexpensive on-chip electrochemical devices. Thick carbon films are commonly prepared by printing commercial carbon ink formulations containing different binding polymers and adhesion promoters that depend on the manufacturer and that often make the electrochemical performance of the resulting devices to differ significantly. [7] By contrast, thin carbon films are produced with nearly pure carbon materials making the electrochemical performance of the device to be more steadfast.So far, a variety of procedures have been described to develop thin carbon films on technologically relevant substrates, which mostly fall into two main categories, namely, gas phase deposition and liquid phase deposition, followed by carbonization. Gas phase deposition techniques, including physical [8,9] and chemical vapor [10][11][12][13] deposition, produce thin carbon films of superior quality displaying a wide range of structures and properties between those of graphite [9] and diamond [12] or carbon nanomaterials such as nanotubes [11] or graphene. [13] On-chip platforms including highly sensitive electrochemical sensors [14] or supercapacitors [15] are achieved by patterning these thin carbon films via microfabrication techniques such as lithography. Nevertheless, these film deposition methods require sophisticated equipment as well as stringent deposition conditions, such as vacuum or an inert atmosphere, gas flow adjustments, and relatively high carbonization temperatures, which are demanding and costly. Liquid-phase deposition techniques mainly comprise coating a substrate with a polymer precursor followed by carbonization. [16,17] This approach benefits from Carbonaceous materials are extensively applied to the development of electrochemical devices for electroanalysis, energy conversion, and storage or electrocatalysis because of their rather unique features that include high chemical stability, low cost, and wide potential window. Furthermore, they are processed into thick or thin-film structures onto different substrates for producing electrode devices whose widespread use, however, is hampered by the film composition and the poor mechanical stability. Here the application of carbon/ silica composites is shown to produce miniaturized thin-film electrodes, which stand out for their robustness and can thus be used re...

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