G. Soubercaze-Pun

Paul Sabatier University - Toulouse III, Tolosa de Llenguadoc, Midi-Pyrénées, France

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Publications (5)0 Total impact

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    ABSTRACT: Wide bandgap devices such as AlGaN/GaN High Electron Mobility Transistors (HEMT) grown on silicon carbide (SiC) substrate are investigated. Low frequency noise (LFN) measurements have been carried out to evaluate the structural perfection of dual gated HEMT devices featuring 0.25x2x75µm² gate area: generation-recombination (GR) processes are evidenced. Two sets of GR-bulges related respectively to AlGaN/GaN interface and quantum well are identified. Each GR-bulge is composed of two GR centers. The devices are then characterized in a temperature controlled oven, and these GR centers are extracted from LFN spectra versus temperature. Activation energies of the defects located at the AlGaN/GaN interface are measured at 0.38±0.05eV and 0.21±0.05eV using Arrhenius plots under saturated biasing conditions. Equivalent activation energies are extracted under ohmic biasing conditions. These results are compared with SIMS measurements, using the deuterium in diffusion condition as a probe to integrally explore the presence of defects throughout the AlGaN-GaN HEMT structure. Large concentrations of deuterium (more than 10E20 D concentration per cm3) are measured at the AlGaN/GaN interface and in the 2DEG layer, thus proving the presence of numerous vacations at the AlGaN/GaN interface as well as in the 2DEG. From the confrontation with previously published results, the defects might be assigned to the nitrogen vacancy and to MgGa-VN complexes.
    07/2007;
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    ABSTRACT: Although GaN technologies were initially developed for solid state source amplifiers, it was recently demonstrated that AlGaN/GaN HEMT transistors were also suitable for low noise applications such as LNA (Tartarin et al., 2005). The frequency synthesis is not yet widely explored for these technologies. In this paper the design of a low phase noise X-band oscillator is proposed. The low frequency noise performance and the residual phase noise, as well as dynamic S-parameters were carried out on AlGaN/GaN HEMT grown on SiC. A large-signal modeling technique is also presented. The reduced complexity and the good accuracy of our large signal model permits an efficient circuit design, without intensive knowledge of the technological device parameters. These characterization and modeling tools are used for the design of an 1-stage oscillator working at 10 GHz delivering 20dBm
    Microwave Symposium Digest, 2006. IEEE MTT-S International; 07/2006
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    ABSTRACT: Newly developed GaN technology offers great potential for military and space, as well as some high volume applications. The devices are grown on different substrates (sapphire, silicon and silicon carbide), involving differences on the performances, price, and technological complexity. The design of a fully integrated transceiver in such a technology necessitates great noise performances for the linear (low noise amplifiers, LNA) and non-linear (voltage controlled oscillator, VCO) applications. The low noise figure already published on this technology up to X-band, associated to the capability to handle high power levels avoid the integration of a limiter stage that deteriorates the overall noise figure in conventional architectures. The low frequency noise performances are useful both for the technology assessment (maturity's indicator) and for the non-linear circuit design (conversion to phase noise around the carrier). This paper presents the noise performances of AlGaN/GaN HEMT grown on SiC substrate. Low frequency noise contributors in the ohmic and saturated regime are discussed. Residual phase noise characterization at 10 GHz correlates the results about the noise sources involved, and linear high frequency noise figure measurements are also presented, targeting respectively VCO and LNA applications
    Gallium Arsenide and Other Semiconductor Application Symposium, 2005. EGAAS 2005. European; 11/2005
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    ABSTRACT: AlGaN/GaN HEMTs are promising devices not only for high frequency power amplification but also for non-linear applications such as VCO. Therefore an assessment of their low frequency noise (LFN) is needed since it can be up-converted around the RF carrier. We have therefore compared different devices either made on sapphire or silicon in order to know which ones feature the lowest LFN. This study involves static and low frequency noise measurements (two different LFN set-up will be used and compared). GaN HEMT devices featuring several gate dimensions have been measured for different biasing conditions both in ohmic and saturation regime. We have compared sapphire based devices with silicon based ones with respect to their LFN levels. In a second part of this work, we report on some reliability results of HEMT on sapphire substrates: identification of defects has been achieved with the help of static measurements, and we make use of low frequency noise as well as physical simulation in order to understand the operating mode of the device. For the first time, we correlate the γ of the 1/fγ LFN spectrum with transport mechanisms of the carriers: we found that γ strongly depends on the carriers conduction path. This hypothesis has been checked for HEMT on silicon substrate.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    05/2004;
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    ABSTRACT: This paper deals with the carrier’s transport mode involved in AlGaN/GaN HEMT grown on sapphire substrate according to biasing conditions. Low frequency noise measurements on the drain current source are found to be closely related to the path of the carriers occurring in the two dimensions electron gas (2DEG) and in the AlGaN layer: thus a correlation is found between the 1/f γ frequency index γ and the biasing condition of the device. Physical modelling is used in order to corroborate the γ dependence with the transport mechanism of the carriers, thanks to DC simulations and energetic band diagrams analysis.