Highlighting trapping phenomena in microwave GaN HEMTs by low-frequencyS-parameters

Abstract

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

Trap-related frequency dispersion of zero-bias microwave responsivity at low temperature in GaN-based self-switching diodes

“…Interfacial traps were also detected in similar devices as a result of frequency dispersion in capacitance and conductance [17]. As will be shown in the following, the characteristic time found in our measurements at the higher temperatures exhibits a similar temperature dependence to that of bulk traps [9,10]. However, that is not the case of our results at low temperature, whose behavior fits much better the case of a spread of relaxation times instead of a single one.…”

“…The objective of this paper is to analyze the impact of temperature on the microwave detection capabilities of GaN SSDs, in particular on the responsivity, which exhibits an unexpected behavior that we attribute to the presence of traps, also reflected in the DC I-V curves. Impedance measurements, proved to be a powerful tool to identify trapping effects [9,10,17,28], are employed to get more insight into the properties of the traps present in SSDs. The results evidence the presence of both bulk and surface traps, the latter involving a spread of relaxation times [29,30], consistent with the presence of lateral surface states at both sides of the channel.…”

Analysis of trap states in AlGaN/GaN self-switching diodes via impedance measurements

“…Second, their slow nature causes frequency dispersion, thus limiting their dynamic performance. Recently, a wide variety of techniques have been used to investigate the behavior of trapping mechanisms [2][3][4], one of the most popular methods consisting of impedance measurements, allowing to find the activation energy (E a ) of charge traps. Both surface and bulk traps in transistors are usually modelled as an RC circuit, either in parallel or in series with the classic small-signal equivalent circuit, thus capturing the frequency dispersion of the output impedance of the devices.…”

Charge-conservative GaN HEMT nonlinear modeling from non-isodynamic multi-bias S-parameter measurements

“…During the last years, modeling developments were mainly focused on the impact of LF dispersive phenomena on the conduction current [4,[6][7][8][9][10][11]. Lately, attention has been drawn to the influence that charge trapping may have on the displacement current modeling flow [12], and the consequent impact on linearity performance prediction under modulated excitation, namely the prediction of intermodulation distortion (IMD) products.…”