ELEGAN

Advanced characterisation of ELEctronic properties of GAllium Nitride based devices

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 Obiettivo del progetto (Objective)

'The project is focused on the characterisation and modelling of a new generation of wide band gap (WBG) GaN technology and devices for which strong impacts in terms of performance, reliability and robustness are expected. GaN material, despite its extraordinary properties and the strong demand of some markets (see following paragraphs) is still at R&D stage, mainly for reasons linked to a poor understanding of electrical effects in the material. One of the main identified bottleneck relates to the dispersive phenomena observed which limits substantially the device performances. ELEGAN will address directly the study and understanding of the trapping effects in field effect GaN-based transistors. Those effects are detrimental to device operation for they are not only inducing lag effects (dispersive phenomena) between the gate command and the resulting output current-voltage I-V characteristics, but also have a strong impact on device breakdown voltage. The objective of ELEGAN is to understand the trapping effects in field effect GaN-based transistors. The achievement of such objective will result in contributing to several strong socio-economic impacts: - strengthen the EU competitiveness in various sectors: telecom, space, electrical conversion (car industry, consumer electronics etc.); - lower the power consumption of Electronic products; - set up future standards in microwave or electrical conversion. To reach this objective, the fellow will undertake different type of research activities: in particular, he will carry out electrical characterisation (DC IV measurement, pulse IV, C-V) and he will use state of the art physical transport simulator to determine the origin and location of the deep level electronic traps. These research activities are detailed in the following paragraphs.'

Introduzione (Teaser)

In high-frequency and high-power electronics, gallium nitride (GaN) is set to take over as silicon-based devices reach their limits. EU-funded scientists sought to gain a better understanding of its physical properties, and their findings helped mature the new technology.

Descrizione progetto (Article)

The superiority of GaN stems from its unique material and electronic properties, making it attractive for electronics and optoelectronics applications. In addition to operating at higher voltages and currents, the switching capability of GaN transistors is up to 10times faster than that of their silicon equivalents. High electron mobility transistors based on GaN have also shown an improvement by a factor of 10in the power density produced at microwave frequencies.

While the achieved performance reveals tremendous potential for GaN in a variety of applications, GaN devices have yet not replaced existing technologies. Technical issues such as electron trapping remain to be consistently solved. Drawing on the research resources of the III-V Lab in France, EU-funded researchers availed themselves of state-of-the-art equipment to understand the origin and physical mechanisms involved in trapping effects.

Within the framework of the 'Advanced characterisation of electronic properties of gallium nitride based devices' (ELEGAN) project, they found that the influence of traps is greater in transistors operating at high frequencies. In transistors based on thin layers of GaN grown on other materials such as silicon nitride, the drain current was significantly reduced as a result of the trapping effects. The so-called current collapse along with voltage swings ultimately affected the output power.

Based on these findings, ELEGAN project fellows prepared GaN-based power bar transistors with normally-off operation. Normally-off operation was strongly desired for the first industrial generation of electrical vehicles designed within the 'Nanoelectronics for an energy-efficient electric car' (E3CAR) project. Moreover, the developed power bar transistors reached the largest drain current ever demonstrated.

GaN-based transistors did not only prove to have the characteristics necessary to cope with the advanced power supply and power management designs of E3CAR.ELEGAN has also revealed that market penetration of GaN is well within the realms of near-future possibility, offering exciting new prospects for the European semiconductor industry.