Charles Surya

The effect of hot-electron injection on the properties of flicker noise in n-channel MOSFETs

Abstract We have studied the degradation of drain current and the properties of flicker noise in n-channel Lightly-Doped Drain (LDD) MOSFETs due to hot-electron injection. The two types of devices examined were shallow double-diffused drain and deep double-diffused drain MOSFETs. It was found that the flicker noise level is highly sensitive to hot-electron injection. The increase in flicker noise and drain current degradation in the shallow double-diffused drain devices were significantly more than the deep double-diffused drain devices, indicating improved hot-electron hardness in the latter. However, the pre-stressed flicker noise magnitudes in the deep double-diffused drain transistors were about two orders of magnitude higher than the shallow double-diffused drain transistors. This is possibly due to creation of defects during the high energy phosphorus implantation step in the fabrication of the deep drain junction.

Spectral and random telegraph noise characterizations of low-frequency fluctuations in GaAs/Al/sub 0.4/Ga/sub 0.6/As resonant tunneling diodes

The origin of low-frequency noise in resonant-tunneling diodes is investigated through spectral and time-domain characterizations over a wide range of temperatures and biasing conditions. The experiments were conducted on devices fabricated on GaAs/Al/sub 0.4/Ga/sub 0.6/As material system. Detailed analyses on the temperature and bias dependences of the random telegraph noise and Lorentzian structures in the noise power spectral densities showed that the low-frequency excess noise arises from hopping conduction of electrons from the emitter to the quasi-bound states in the quantum well. The capture of an electron by a trap in the energy barrier causes fluctuations in the transmission coefficient of the electron due to the modulation of the barrier potential. >

Theory and experiments on flicker noise in In0.53Ga0.47As/AlAs/InAs resonant tunneling diodes

We studied 1/fγ noise in strained‐layer In0.53Ga0.47As/AlAs/InAs resonant tunneling diodes from 77 to 293 K and observed variations over temperature for both the noise magnitude and the spectral shape. Analyses of our data indicated a thermally activated noise process. Our measurement further showed that the current noise magnitude SI varied approximately as I2 at room temperature, but deviated significantly from an I2 dependence at low temperatures. Such observations are accounted for by a model based on the capture and emission of electrons by interface states through thermal activation. These traps cause fluctuations in the tunneling current by modulating the barrier potential and thus the transmission coefficient.

Observation of random‐telegraph noise in resonant‐tunneling diodes

We report the observation of random‐telegraph noise in GaAs/Al0.4Ga0.6As resonant tunneling diodes. Measurements made on our devices from 57 to 70 K revealed discrete switching events with step heights ranging from 6 to 20 μV. Our studies indicated that the 20‐μV switching sequences correspond to two‐state thermally activated processes involving a single trap. At a bias of −0.4 V, the capture and emission activation energies of this trap are 81 and 51 meV, respectively, implying that the trap is located in the barrier. Our results suggest that the noise arises from transmission coefficient fluctuations due to hopping conduction of carriers through the barrier.

A model for low frequency excess noise in Si-JFETs at low bias

Abstract Spectral analyses of the fluctuating drain-source voltages in n - and p -channel Si-JFETs at low bias conditions revealed generation-recombination (G-R) noise over a temperature range of 150–300 K in both types of devices. The corner frequencies f C and the low frequency plateau values of the Lorentzian spectra were used to study the nature of the noise. In the n -channel device, f C was strongly temperature dependent; an activation energy, E C − E T , of approximately 0.36 eV was obtained from the Arrhenius plot. For the p -channel device, a much higher corner frequency of 20–30 kHz was measured. Based on the experimental results we are led to consider a model for low frequency noise in JFETs that accounts for fluctuations in the channel thickness, and the correlated fluctuations in the number and the mobility of carriers. The relative significance of the three noise mechanisms was found to depend strongly on temperature, doping concentrations, device dimensions, and the energy level of the recombination centers.

Studies of flicker noise in In0.53Ga0.47As/AlAs/InAs resonant tunneling diodes

Abstract We report on low-frequency noise studies of strained-layer In0.53Ga0.47As/AlAs/InAs resonant tunneling diodes over a frequency range of 10 Hz–100 kHz and a temperature range of 77–293 K. The noise was found to be dominated by flicker ( 1 f γ ) noise for frequencies below 10 kHz, with the frequency exponent γ varying from 0.75 to 1.1 over temperature. Our results indicate that the 1 f γ noise originates from thermal activation of electrons from the conduction band to interface states at the heterojunctions, with a distribution of activation energy that peaks at about 0.27 eV.

Low‐frequency excess noise in YBCO thin films near the transition temperature

We conducted detailed systematic studies on the properties of low frequency noise in YBCO thin films near the transition region. Detailed studies on the dependences of the low frequency noise on the biasing current, ∂R/∂T, and spatial correlation were conducted. It was shown that the measured voltage noise power spectra were proportional to I2 and (∂R/∂T)2, and were correlated over a spatial separation of 300 μm. Also, the voltage noise power spectral densities exhibit a lower cutoff frequency of 5 Hz, in excellent quantitative agreement with the cutoff frequency predicted by the Thermal Fluctuation model. The experimental results provide strong evidence that the low frequency excess noise in the device originated from equilibrium temperature fluctuations.

Thermal fluctuations in Y-Ba-Cu-O thin films near the transition temperature

Detailed studies on the properties of low frequency noise in Y-Ba-Cu-O thin films in the transition region were conducted. Our experimental results showed that the low frequency excess noise exhibited a lower cutoff frequency of about 5 Hz, below which the noise power spectra were independent of frequency. At T close to T/sub C/ and at small current biases the voltage noise power spectra were proportional to I/sup 2/, (/spl part/R//spl part/T)/sup 2/ and inversely proportional to the volume of the device, /spl Omega/. In addition, low frequency noise measured from two segments separated by a distance of 300 /spl mu/m was found to be correlated. The lower cutoff frequencies computed for both the noise power spectra and the frequency dependent correlation function, according to the thermal fluctuation model, were found to be in good agreement with the experimental values. The experimental results provide strong evidence that the low frequency excess noise in the device originates from equilibrium temperature fluctuations for small T and T/spl sime/T/sub C/. >

Comment, on "A 1/f noise technique to extract the oxide trap density near the conduction band edge of silicon" [with reply]

For the original article see ibid., vol.36, no.9, p.1773-82 (1989). The commenters show that, contrary to the calculations in the above-titled paper by R. Jayaraman and C.G. Sodini, the correlated noise power spectra of number and surface mobility fluctuations in n-channel MOSFETs are functions of the relative densities of the positive and neutral traps at the Si-SiO/sub 2/ interface. The authors, along with B.J. Gross, disagree with the commenters assessment and support their calculations. The contend that the distribution of active traps assumed by the commenters is not representative of the distribution active in real MOSFET devices. >

G‐R noise in GaAs/Al0.4Ga0.6As resonant tunneling diodes

Low‐frequency excess noise was measured from GaAs/Al0.4Ga0.6As resonant tunneling diodes. The noise power spectra of the fluctuating voltage across the devices exhibit two distinct bumps in a 1/f background. One dominates at T≳210 K and the other one at 140 K<T<180 K. The magnitudes and the characteristic frequencies of the bumps demonstrated significant temperature dependences. In this paper we show that capture and emission energies of the traps can be obtained from the temperature and bias dependences of the voltage noise spectra. Our experimental results showed that the high temperature G‐R noise has a emission activation energy of ∼400 meV and capture activation energy of ∼200 meV, suggesting that the noise originates from DX centers. The origin of the low temperature G‐R noise is unclear. In addition, our analyses indicated that the high temperature G‐R noise involves a hopping process whereas the low temperature G‐R noise may arise from an equilibrium trapping and detrapping process.