Low Frequency Drain Current Noise Research Articles

Ionic screening effect on low-frequency drain current fluctuations in liquid-gated nanowire FETs

The ionic screening effect plays an important role in determining the fundamental surface properties within liquid–semiconductor interfaces. In this study, we investigated the characteristics of low-frequency drain current noise in liquid-gated nanowire (NW) field effect transistors (FETs) to obtain physical insight into the effect of ionic screening on low-frequency current fluctuation. When the NW FET was operated close to the gate voltage corresponding to the maximum transconductance, the magnitude of the low-frequency noise for the NW exposed to a low-ionic-strength buffer (0.001 M) was approximately 70% greater than that when exposed to a high-ionic-strength buffer (0.1 M). We propose a noise model, considering the charge coupling efficiency associated with the screening competition between the electrolyte buffer and the NW, to describe the ionic screening effect on the low-frequency drain current noise in liquid-gated NW FET systems. This report not only provides a physical understanding of the ionic screening effect behind the low-frequency current noise in liquid-gated FETs but also offers useful information for developing the technology of NW FETs with liquid-gated architectures for application in bioelectronics, nanosensors, and hybrid nanoelectronics.

Characterisation and modelling of parasitic effects and failure mechanisms in AlGaN/GaN HEMTs

This work is a study of the degradations of AlGaN/GaN HEMTs induced by 2000 h of ageing tests. The methodology is based on cross-characterisation analysis. The life tests (HTO 150 °C, HTO 175 °C and HTRB 175 °C and Idq 90 °C) have mainly induced a decrease of the saturation drain current, occurring during the first 50 h, followed by a stabilisation. There is a shift of the pinch-off voltage in the range of 0.1–0.2 V while the Schottky contact is rather stable after ageing. The evolution of the electrical characteristics after ageing does not depend on the bias conditions but rather more on the channel temperature. It seems to be neither field nor current driven. Low frequency drain current noise demonstrates that there is no trap creation and the weak evolution of the 1/ f noise confirms that there is no degradation in the channel. Moreover, pulsed I– V measurements show a weak evolution of gate lag and drain lag rates after ageing. The same degradation mode is demonstrated for all life tests with rather high activation energy of 1.6 eV. The weak evolution of electrical characteristics observed during the life tests cannot be obviously explained by a single physical mechanism and results from a combination of trap-related effects before stabilisation.

ANALYSIS OF LOW FREQUENCY DRAIN CURRENT NOISE IN AlGaN/GaN HEMTS ON Si SUBSTRATE

This paper deals with the analysis of the low frequency drain current noise in gallium nitride FET on silicon substrate. The drain current noise is compared for devices with gate length of 1.5μm and 3.5μm. We discuss two types of noise mechanisms both used as a diagnostic tool: generation-recombination noise and 1/f noise. Measurements in saturation regime have revealed a g-r noise mechanism correlated with the activation of discrete traps. The analysis of the normalized drain current spectral density vs. the normalized gate voltage Vgn=(Vg-Vt)/|Vt| has been studied. In particular, we have pointed out that the evolution of the 1/f noise level strongly depends on the evolution of the gate leakage current. On the basis of the 1/f normalized noise, i.e. the αH/N parameter, GaN HEMT on silicon have demonstrated as low LF noise as GaAs based transistors.

Hot-carrier-induced degradation in short p-channel nonhydrogenated polysilicon thin-film transistors

The effects of low gate voltage |V/sub g/| stress (V/sub g/=-2.5 V, V/sub d/=-12 V) and high gate voltage |V/sub g/| stress (V/sub g/=V/sub d/=-12 V) on the stability of short p-channel nonhydrogenated polysilicon TFTs were studied. The degradation mechanisms were identified from the evolution with stress time of the static device parameters and the low-frequency drain current noise spectral density. After low |V/sub g/| stress, transconductance overshoot, kinks in the transfer characteristics, and positive threshold voltage shift were observed. Hot-electron trapping in the gate oxide near the drain end and generation of donor-type interface deep states in the channel region are the dominant degradation mechanisms. After high |V/sub g/| stress, transconductance overshoot and "turn-over" behavior in the threshold voltage were observed. Hot-electron trapping near the drain junction dominates during the initial stages of stress, while channel holes are injected into the gate oxide followed by interface band-tail states generation as the stress proceeds.

Empirical relationship between low-frequency drain current noise and grain-boundary potential barrier height in high-temperature-processed polycrystalline silicon thin-film transistors

The relationship between low-frequency drain current noise spectral density SI and grain-boundary potential barrier height Vb is investigated in high-temperature-processed polycrystalline silicon thin-film transistors. It is demonstrated that a general empirical relationship exists between SI and Vb indicating that the noise sources are located at the grain boundaries. The implications of the obtained relationship between SI and Vb from the practical viewpoint are discussed.

Effect of Schottky barrier alteration on the low-frequency noise of InP-based HEMTs

For the first time the effect of increasing the Schottky barrier's Al content of InP-based InAlAs-InGaAs HEMTs from 48 to 60% on the low-frequency (LF) drain and gate current noise is investigated. It is shown that the LF gate current noise S/sub IG/(f) for the 60% case decreases by almost three decades, while the LF drain current noise S/sub IDS/(f) stays at the same level. From small coherence values, it can be concluded that drain and gate noise sources can be treated separately which facilitates the LF noise modeling of these HEMTs.

Low-frequency drain current noise behavior of InP based MODFET's in the linear and saturation regime

This paper describes a detailed experimental study of the low-frequency (LF) drain current noise behavior of InP based MODFET's in a broad operation regime, spanning both linear and saturation operation. The noise power spectral density S/sub lD/ of the predominantly 1/f noise is studied as a function of the gate and drain bias. The experimental noise behavior is compared with available analytical models. It is shown that there is a reasonable agreement between the data and the theoretical models in linear operation. However, no accurate theory exists for the saturation regime. Therefore, an empirical analytical description is proposed, which provides a good approximation for the measurement data base. Furthermore, it can be used as a starting point for phase noise simulations in high-frequency nonlinear circuits.