This paper proposes a diagnostic tool dedicated to the analysis of the Schottky Barrier Height (SBH). The proposed method is mainly relevant for studying gate related failure mechanisms in electronic devices. In this case, the SBH of gallium nitride High Electron Mobility Transistors (HEMTs) is investigated in terms of mean SBH's value and dispersion. It is shown that according to given temperature and gate current ranges, linear relationships can be extracted between the mean SBH and the inhomogeneities that appear in forward-biased diode. These behaviors are able to highlight different kind of defects, revealing possible weaknesses of the devices.

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This work focuses on short term and long term time evolution of charges in the context of early identification of failure mechanisms in AlGaN/GaN High Electron Mobility Transistors (HEMTs). High power and high frequency devices are needed for new microwave applications, and large band-gap HEMTs offer a powerful alternative to traditional technologies (Si, GaAs, SiGe etc.); however, reliability issues still hamper the potential of these technologies to push their limits in terms of mean time to failure or junction temperature. This paper contributes to the investigation of transient behaviours of gate and drain currents over a large time scale for gallium nitride HEMTs; a correlation is found between the currents' evolution, in spite of the non-monotonic behaviour, and a model is given through a mathematical relationship. Charges under the gated zone of the transistor are found to evolve with time, and turn into command variations of the electron density in the 2DEG. This work addresses the consequences of charge dependent mechanisms on the drain current's drop, and thus of the output power.

Nitride technologies are widely used for high frequency and high power electronics, and raise a growing interest for robust low noise receivers. However, the stability of DC and RF performances are difficult to achieve, at a cost of technological trade-offs. Among the problems not totally mastered, traps and charges located in the active regions of the transistor induce a large variety of electrical behaviours; some traps are not harmful as they do not affect the transistor performances, some can impact the signal integrity or can raise reliability problems. The paper addresses a method based on low frequency noise (LFN) and random telegraph noise (RTN) measurements crossed with transient measurements and T-CAD simulations to locate the defects, and to evaluate their actual impact on the device integrity. This study is realized on virgin and stressed AlGaN/GaN High Electron Mobility Transistors (HEMT). Charges under the gated zone and at the AlGaN/GaNpassivation interface are identified by noise measurements and by T-CAD simulations.