M. de Murcia

Diffusion and noise in GaAs material and devices

The variation of the diffusion coefficient D(E) versus the electric field strength E is determined at 300 K in n-type GaAs (N/sub D/=3*10/sup -17/ cm/sup -3/), using pulsed high-frequency noise measurements. D(E) is found to increase slightly at low field, then to decrease down to one tenth of its ohmic value near the threshold field. Long (>or=4 mu m) real n/sup +/-n-n/sup +/ Gunn diodes, with an arbitrary doping profile, can be modeled. Comparisons are made, and excellent agreement is found, between experimental and theoretical characteristics of two real diodes, with notch and with gradual doping profiles. The doping profile N/sub D/(x) is shown to have a considerable influence on the diode behavior, in regard to the electric field profile as well as the noise characteristics. Using the impedance field method, the noise current is modeled and found to by very sensitive in the D(E) variation law, in particular in the range of 2.5-4 kV/cm. The agreement between the experimental noise and the computed noise of real diodes is quite satisfactory when using the D(E) determined. >

Low frequency noise characterization in 0.13 μm p-MOSFETs. Impact of scaled-down 0.25, 0.18 and 0.13 μm technologies on 1/f noise

Abstract This paper presents an experimental analysis of the noise measurements performed in 0.13 μm technology p-MOS transistors operating from weak to strong inversion in ohmic and saturation regimes. The 1/ f noise origin is interpreted in terms of carrier number with correlated mobility fluctuations. The contribution of the access resistance noise is noticed for large overdrive voltages. The slow oxide trap density N t ( E F ) and the Coulomb scattering noise parameter α s have been extracted. Then the 1/ f noise level in the three scaled-down p-MOSFETs generations (0.25, 0.18 and 0.13 μm) is compared. The variation of the noise parameter values is discussed with respect to the technology node. The highest oxide trap density is obtained for the thinnest gate oxide. It is concluded that the oxide thinning should lead to noise reduction only if the product t ox 2 . N t is taken into consideration. This trend will be significant in future scaled-down MOSFETs.

1/f noise in 0.18 μm technology n-MOSFETs from subthreshold to saturation

Low frequency noise in 0.18 μm technology n-MOSFETs is investigated in subthreshold, ohmic and saturation regimes. The impact of the channel length on the drain current noise characteristics is studied. The results are analysed as a function of the drain current or gate voltage and compared to the existing noise models. We find that the 1/f noise can be interpreted in terms of carrier number fluctuations. The oxide trap density Nt at the Fermi energy level is evaluated. The significant deviation of the normalised noise amplitude observed at high VGS is attributed to the noise in the access resistances. In deep saturation regime, for gate length device <0.9 μm, the drain current spectral density tends to saturate with the gate overdrive voltage. The noise characteristics calculated with BSIM3v3 noise model are compared with the experimental results and discussed.

1/ƒ and g-r noise in AlGaAs epitaxial layers

Abstract Low frequency noise measurements have been performed in AlxGa1−xAs test structures with x = 0.25 and x = 0.20 at 300 K. For samples with x = 0.25 the excess noise spectra show two Lorentzian shaped g-r contributions and 1/ƒ noise and with x = 0.20 the main noise source is a 1/ƒ component. The results are analysed as a function of the sample length in order to distinguish between bulk and interface noise contributions.

A specific trap level at 78 meV in undoped liquid encapsulated Czochralski grown GaAs–SI materials

In this paper we provided experimental evidence for the presence of a 78 meV trap which is specific of liquid encapsulated Czochralski grown semi‐insulating GaAs. This trap gives rise to a well defined thermally stimulated current peak obeying a monomolecular recombination model and amendable to an accurate differential analysis. The Urbach parameter Ei/kTm is shown to lie well below the usual domain, as it was established for low temperature peaks. The deduced cross section is weak, whatever the polarity involved, and quite adapted to the case of a double acceptor. The thermal activation energy 78 meV is consistent with the optical transitions observed in absorption or photoluminescence whereas it looks different with the deep level transient spectroscopy or photo‐induced transient spectroscopy or temperature dependant Hall results; this discrepancy is explained by the influence in these experiments of neighboring traps of larger cross section. Then it is confirmed that this 78‐meV trap could originate i...

1/f noise measurements in n-channel MOSFETs processed in 0.25 μm technology: Extraction of BSIM3v3 noise parameters

Abstract Low frequency noise has been studied from the weak to strong inversion regime in n-channel MOS transistors. The 1/ f current noise power spectrum density S ID is measured as a function of the drain current and gate voltage with the gate length as a parameter. Analysis of the noise characteristics shows that the channel noise agrees with the mobility fluctuation model and can be predicted in the linear and saturation region using the α H parameter only. Finally, the three parameters NOIA, NOIB and NOIC used in the BSIM3v3 noise model are extracted. Some discrepancies of the noise simulation with the experimental data are observed.

Nonequilibrium thermal noise in GaAs/GaAlAs superlattice miniband

We present the first measurement of non‐equilibrium thermal noise (i.e. hot electron diffusion noise) related to vertical transport in superlattice minibands. Bias dependence of the longitudinal diffusion coefficient has been extracted from experimental data and compared with two models. We show that this coefficient is a clearly decreasing function of the applied electric field, in agreement with theoretical models. This result highlights the potential superiority of superlattices in millimeter wave devices as regards noise.

High frequency noise and diffusion coefficient of hot electrons in bulk Al0.25 Ga0.75 As

Abstract We present experimental results of hot electron noise in Si doped Al 0.25 Ga 0.75 As test structures using pulsed high-frequency noise measurements. Noise temperature and longitudinal diffusion coefficient as functions of field strength are compared with those of Si doped GaAs. We find significant changes at high fields. Results are discussed in regard of electron scattering mechanisms.

Influence of Al content x on hot electron noise in Al/sub x/Ga/sub 1-x/As n/sup +/nn/sup +/ devices: comparison with GaAs

Hot electron noise measurements are performed in Si doped Al/sub x/Ga/sub 1-x/As n/sup +/nn/sup +/ devices, for three different Al concentrations: x=0.15, 0.2, 0.25. Noise temperatures are obtained using a pulsed measurement technique as functions of electric field and frequency. Longitudinal diffusion coefficients D(E) are deduced at 4 GHz. Results are analyzed through the scattering mechanisms which greatly affect the electron velocity properties of Al/sub x/Ga/sub 1-x/As materials. Comparisons with n/sup +/nn/sup +/ GaAs devices are made. >

Excess noise in Al0.25Ga0.75As epitaxial layers

Low frequency noise measurements have been performed in Al0.25Ga0.75As test structures at 300 K. The excess noise spectra show two Lorentzian shaped g‐r contribution and 1/f noise. The results are analyzed as a function of the sample length in order to distinguish between bulk and interface noise contributions.