1,721,019 research outputs found
Correlation Between Surface-state Density and Impact Ionization Phenomena In Gaas-mesfets
No full textGaAs MESFET's passivated with PECVD SiN show a lower surface-state density in comparison with SiO passivated devices, as deduced from g(m)(f) dispersion curves. Lower carrier multiplication due to impact ionization phenomena in the active channel and consequently a higher breakdown voltage are observed in SiO passivated samples. These effects are attributed to a lower peak electric field near the drain edge of the gate, deriving from an accumulation of negative surface charge
Low-Frequency Noise Characterisation of AlGaAs/GaAs HBT’s
No full textIn the present paper we evaluated the fabrication process of AlGaAs/GaAs heterojunction Bipolar Transistors (HBT's) by means of low frequency noise characterizations carried out in the 100Hz-100kHz frequency range. We investigated the spectra of the base current fluctuations. The obtained results are compared with the data reported in the literature. The fabrication technology and the experimental set-up are briefly described
Frequency dispersion of transconductance: a tool to characterise deep levels in III-V FETs
No full textFrequency dispersion of transconductance g(m)(f) has been exploited to quantitatively investigate the properties of deep traps in III-V FET devices, namely DX centres in GaAs/AlGaAs HEMTs. This method requires simple data acquisition and elaboration and is applied directly to packaged devices. Thermal emission energy E(a) = 0.46 eV and capture cross-section sigma = 3.10(-14) cm2 have been obtained for DX centers in AlGaAs, in good agreement with published data. By increasing V(DS), we measured also an E(a) decrease due to hot electron trapping by the DX centres
Impact Ionization In Gaas-mesfets - Comments
No full textIn the above-named work (see ibid., vol.11, p.113-15, March 1990), Hui et al. proposed a method to measure impact ionization current in GaAs MESFETs and evaluated the impact ionization coefficient alpha /sub n/ in GaAs. For electric fields greater than approximately 1.5*10/sup 5/ V-cm/sup -1/, alpha /sub n/ can be fitted to the equation alpha /sub n/=4.0*10/sup 6/*exp (-2.3*10/sup 6//E). In the present work, the commenters performed careful measurements of gate current I/sub g/ in GaAs MESFET devices similar to those used by Hui et al., and they show that the ionization coefficient still fits the above equation down to alpha /sub n/=10/sup -4/ cm/sup -1/. These results extend the previous data by three orders of magnitude. In a reply, the original authors affirm that the commenters have significantly improved the accuracy of the data previously presented
Interactions between DX centers and hot electrons and holes in AlGaAs/GaAs heterostructure field-effect transistors
No full textUsing power Al0.25Ga0.75As/GaAsAl0.25Ga0.75As/GaAs heterostructure field-effect transistors (HFETs) and both electrical and electroluminescence measurements, we show here that while at room temperature the electron and hole capture processes at the DX centers present in the AlGaAs are in equilibrium, and therefore no charge buildup leading to drifts in the HFET characteristics may take place, under cryogenic conditions (T<100 K), where the electron and hole capture cross sections of the DX centers are very different, two competing processes of hole and hot electron capture lead to bias-dependent, negative, recoverable HFET threshold voltage shifts
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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