This paper presents an original characterization method of trapping phenomena in gallium nitride high electron mobility transistors (GaN HEMTs). This method is based on the frequency dispersion of the output-admittance that is characterized by low-frequency S-parameter measurements. As microwave performances of GaN HEMTs are significantly affected by trapping effects, trap characterization is essential for this power technology. The proposed measurement setup and the trap characterization method allow us to determine the activation energy Ea and the capture cross-section σnof the identified traps. Three original characterizations are presented here to investigate the particular effects of bias, ageing, and light, respectively. These measurements are illustrated through different technologies such as AlGaN/GaN and InAlN/GaN HEMTs with non-intentionally doped or carbon doped GaN buffer layers. The extracted trap signatures are intended to provide an efficient feedback to the technology developments

This paper presents a detailed trap investigation based on combined pulsed I/V measurements, drain current transient (DCT) measurements and low-frequency dispersion measurements of transconductance (LF Y21) and output conductance (LF Y22). DCT characterization is carried out over a 7-decade time scale. LF Y21and Y22measurements are carried out over the frequency range from 100 Hz to 1 GHz. These combined measurements were performed at several temperatures for AlGaN/GaN high electron mobility transistors under class AB bias condition and allowed the extraction of the activation energy (Ea) and the capture cross section (σc) of the identified traps. Extensive measurements of these characteristics as a function of device bias are reported in this work to understand the dynamic trap behavior. This paper demonstrated a correlation between LF small-signal (LF Y21and Y22) and large-signal voltage steps (DCT) results. These measurements allow identifying the same 0.64 eV deep level, attributed to a native defect of GaN, possibly located in the buffer layer.

This paper presents a characterization method of traps in GaN HEMTs, based on the frequency dispersion of the output-admittance characterized by low-frequency S-parameter measurements. As RF performances of GaN HEMTs are significantly affected by trapping effects, trap characterization is essential for this power technology. The proposed measurement setup and extraction method allow us to derive the activation energy E a and the capture cross section σ n of the identified traps. A 0.25µm gate length InAlN/GaN HEMT was characterized. A trap was identified with an activation energy of 0.38eV, a capture cross-section of 1.73x10 -16 cm 2 , and a field dependency of the emission rate. These results are used to give an efficient feedback to the technology developments.

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Time-domain pulsed I-V measurements dedicated to characterising and modelling the time-dependent trapping phenomena of wide band-gap AlGaN/GaN high electron mobility transistors (HEMTs) are presented. The influence of temperature, electric field and their mutual interaction on trap activation and time constants are investigated and illustrated in the case of 2 × 75 × 0.15 µm 2 AlGaN/GaN HEMTs from the III-V Lab. These measurements show that the most influential parameter on trap activation is the electric field induced by the highest drain voltage V DS-max reached during a pulse sequence, which leads to the drain current collapse. These characterisations are intended to develop and improve new nonlinear models of GaN HEMTs, taking into account the dynamics of traps for modulated signals.Introduction: AlGaN/GaN high electron mobility transistors (HEMTs) are the most promising candidates for future wireless and radar applications. The intrinsic material properties of GaN such as high electron mobility, wide band-gap and high electron saturation velocity give it superiority over its predecessors like the Si and GaAs devices. Despite the fact that GaN technologies are already on the commercial market, mainly for applications below the X-band, many issues still need to be addressed. Among these, one of the most important issues is the drain current collapse also called kink effect that directly affects the output power, gain and RF transitions of microwave devices under pulse modulated signals.A similar behaviour was reported for GaAs devices [1] where it is caused by impact ionisation, which leads to a sudden rise in the drain current. This explanation is not well suited for GaN devices due to their high breakdown voltage although it can be true at very low temperatures [2]. Kink effect in GaN HEMTs is mainly attributed to carrier trapping [3]. In this Letter, a series of I-V measurements are performed under DC and pulsed modes to characterise the influence of the key parameters involved in carrier trapping, which are temperature and drain voltage.