Generation-recombination Noise Research Articles

High-responsivity, self-driven visible-near infrared Sb2Se3 nanorod array photodetector.

Anisotropic antimony selenide (Sb2Se3) semiconductor has received considerable attention due to its unique one-dimensional crystal structure and corresponding superior and anisotropic optical and electronic properties. It is a promising material for a wide range of applications related to electronics and optoelectronics. Herein, we demonstrate a high-performance and self-powered Sb2Se3 nanorod array-based core/shell heterojunction detector fabricated on glass substate. The detector shows a wide spectral photoresponse range from visible to near-infrared (405-980 nm). The detector yields a detectivity of as high as 2.06×1012 Jones in the visible light (638 nm) and that of 1.82×1012 Jones (830 nm) at zero bias. Due to the strong built-in filed and excellent carrier transport, the detector exhibits ultrafast response speed at both rise (30 μs) and decay (68 μs) processes. Further analysis demonstrates that the noise is mainly generated from the 1/f noise in the low frequency range, while it is affected by the shot noise and generation-recombination noise in high frequency.

Low‐Frequency Electronic Noise in Quasi‐2D van der Waals Antiferromagnetic Semiconductor FePS3—Signatures of Phase Transitions

AbstractLow‐frequency current fluctuations, i.e., noise, in the quasi‐2D van der Waals antiferromagnetic semiconductor FePS3 with the electronic bandgap of 1.5 eV is investigated. The electrical and noise characteristics of the p‐type, highly resistive, thin films of FePS3 are measured at different temperatures. The noise spectral density is of the 1/f‐type over most of the examined temperature range but reveals well‐defined Lorentzian bulges, and increases strongly near the Néel temperature TN = 118 K (f is the frequency). Intriguingly, the noise spectral density attains its minimum at temperature T ≈ 200 K, which is attributed to an interplay of two opposite trends in noise scaling—one for semiconductors and another for materials with the phase transitions. The Lorentzian corner frequencies reveal unusual dependence on temperature and bias voltage, suggesting that their origin is different from the generation—recombination noise in conventional semiconductors. The obtained results are important for proposed applications of antiferromagnetic semiconductors in spintronic devices. They also attest to the power of the noise spectroscopy for monitoring various phase transitions.

Impact of Hot Carrier Aging on the 1/f and Random Telegraph Noise of Short-Channel Triple-Gate Junctionless MOSFETs

The low-frequency noise of short channel triple-gate junctionless (TG JL) MOSFET has been investigated in the frequency and time domains before and after hot carrier aging (HCA). The objective of this work is to investigate the interaction between HCA/flicker noise (1/f noise) and random telegraph noise (RTN) of short channel length device (L = 25 nm) exhibiting high density of interface traps. Significant variation in the noise spectral density has been observed between the fresh and the stressed device, related to the occurrence of generation-recombination (g-r) noise. Gate voltage dependence of g-r noise has been observed, assigned to gate dielectric traps and interface traps. In the fresh device, the noise is dominated by 1/f noise and multiple level RTN due to interface traps. In the stressed device, the 1/f noise is overlaid by multiple level RTN due to traps in the gate dielectric and at the gate insulator-silicon interface. The multiple level RTN relative amplitude can be described by the generic carrier number with correlated mobility fluctuations model as for the two level RTN detected in long channel devices (L = 65 and 95 nm).

Low frequency noise in P-InAsSbP/n-InAs infrared light emitting diode-photodiode pairs

Low frequency noise in P-InAsSbP/n-InAs infrared light emitting diode- photodiode pairs is investigated for the first time at 300 K. It is shown that photocurrent fluctuations under LED illumination are smaller than photocurrent fluctuations under a black body illumination. When the photodiode is illuminated by LED, the spectral noise density follows the 1/f dependence. In the case of a black body illumination we observe a significant contribution of generation-recombination noise.

Relaxation processes in silicon heterojunction solar cells probed via noise spectroscopy

We have employed state-of-the-art cross-correlation noise spectroscopy (CCNS) to study carrier dynamics in silicon heterojunction solar cells (SHJ SCs). These cells were composed of a light absorbing n-doped monocrystalline silicon wafer contacted by passivating layers of i-a-Si:H and doped a-Si:H selective contact layers. Using CCNS, we are able to resolve and characterize four separate noise contributions: (1) shot noise with Fano factor close to unity due to holes tunneling through the np-junction, (2) a 1/f term connected to local potential fluctuations of charges trapped in a-Si:H defects, (3) generation-recombination noise with a time constant between 30 and 50 μs and attributed to recombination of holes at the interface between the ITO and n-a-Si:H window layer, and (4) a low-frequency generation-recombination term observed below 100 K which we assign to thermal emission over the ITO/ni-a-Si:H interface barrier. These results not only indicate that CCNS is capable of reveling otherwise undetectable relaxation process in SHJ SCs and other multi-layer devices, but also that the technique has a spatial selectivity allowing for the identification of the layer or interface where these processes are taking place.

Generation-recombination and 1/f noise in carbon nanotube networks

The low-frequency noise is of special interest for carbon nanotubes devices, which are building blocks for a variety of sensors, including radio frequency and terahertz detectors. We studied noise in as-fabricated and aged carbon nanotube networks (CNNs) field-effect transistors. Contrary to the majority of previous publications, as-fabricated devices demonstrated the superposition of generation-recombination (GR) and 1/f noise spectra at a low-frequency range. Although all the devices revealed identical current–voltage characteristics, GR noise was different for different transistors. This effect is explained by the different properties and concentrations of trap levels responsible for the noise. Unexpectedly, exposure of these devices to the atmosphere reduced both the resistance and GR noise due to nanotube's p-doping by adsorbed water molecules from the ambient atmosphere. The presence of the generation recombination noise and its dependences on the environment provides the basis for selective gas sensing based on the noise measurements. Our study reveals the noise properties of CNNs that need to be considered when developing carbon nanotubes-based selective gas sensors.

Noise behavior of vertical tunnel FETs under the influence of interface trap states

A detailed analysis of low frequency noise behavior of two different vertical TFETs namely n ​+ ​pocket VTFET and dual MOS capacitor (D-MOS) VTFET is presented in this work. Such analysis is performed to understand the limiting factors of their operations. The effect of the presence of both uniform and Gaussian type of interface trap charge distributions on the electrical performance of the devices under consideration are considered in the TCAD simulation study. The results report that the Flicker noise is dominant at low frequency whereas at high frequency, the diffusion noise is the superior noise component. The generation-recombination noise is found to be significant in the entire frequency range considered for the analysis. Lastly, comparison has been done on net drain current noise spectral density (Sid) of some published work and this work.

Detailed low frequency noise assessment on GAA NW n-channel FETs

Low frequency noise (LFN) studies are carried out on n-channel gate all around nanowire (GAA NW) FETs. Measurements both as a function of applied polarisation at fixed temperature and conserving the same drain current bias points as a function of temperature are performed, to investigate the predominant flicker noise fluctuation mechanism and to execute low frequency noise spectroscopy allowing to identify the active traps in the depletion area of the devices. The good correlation between the normalized drain current noise SId / Id2 and the transconductance to drain current ratio squared (gm/Id)2 enables to establish that the 1/f noise is related to the carrier number fluctuations mechanisms for all investigated temperatures. The study of the generation recombination (GR) noise as a function of temperature confirms the presence of a GR component for which the characteristic frequency is independent on the applied voltage and present variation with the temperature, suggesting that they are related to active traps located in the Si film. Active traps related to hydrogen and divacancies were identified.

The transition from generation–recombination noise in bulk semiconductors to discrete switching in small-area semiconductors

Scaling down the dimensions of Metal–Oxide–Semiconductor​ Field-Effect Transistors (MOSFETs) evinces discrete switching usually referred to as random telegraph signal (RTS). Such RTSs are usually attributed to the capture and emission of charge carriers by a single active trap located in an oxide layer. Machlup calculated the noise spectrum caused by these charge carriers based on probabilistic arguments. In this paper, we derive Machlup’s noise spectrum differently: the g–r​ noise is attributed to a random succession of elementary g–r pulses. This enables g–r bulk noise to be interpreted in terms of the numbers of traps. The transition from g–r bulk noise to discrete switching is found by reducing the number of traps to just one single active trap. The resulting g–r noise spectrum is shown to be equivalent to Machlup’s noise spectrum. The probability of an overlap of succeeding g–r pulses is calculated. Such an overlap is attributed to occupation of an empty single trap by an electron transferred from a neighboring trap. We simulate a g–r pulse train and find a large variety of patterns similar to those observed in MOSFETs. Excluding overlapping g–r pulses, the up-and-down distribution of succeeding g–r pulses is estimated.

Investigation of N+ pocket-doped junctionless vertical TFET and its digital inverter application in the presence of true noises

This paper reports the investigation of conventional junctionless tunnel FET (JL-TFET) and N+ pocket-doped junctionless vertical tunnel FET (JL-VTFET). The investigation is done by analyzing the effect on the ID–VGS characteristics (a) under a wide range of temperature and (b) in the presence of acceptor interface trap charges. This work also examines the performance of noise and its impact on the digital inverter. Comparison has been made on the TCAD simulated results of both the devices. It is observed that the degradation of drain current (ID) is less in JL-VTFET and also it has better noise performance than that of conventional JL-TFET. Its net drain current noise spectral density (Sid) reaches 10–15 A2/Hz till 1 MHz and decreases with further increase in frequency. The contributions of generation–recombination noise and flicker noise are found to be more in low and moderate frequency, whereas diffusion noise dominates at high frequency. Furthermore, the impact of interface traps is studied using complementary JL-VTFET digital inverter application and compared with the one without interface traps. The transient characteristics show an average delay of 15 ps and 27 ps in the absence and presence of interface traps, respectively.

Low Frequency Noise Analysis of Single Gate Extended Source Tunnel FET

This paper presents the analysis of noise in Single Gate Extended Source TFET (SG-ESTFET) considering the absence and presence of interface trap charges, when the device is subjected to scaling and variation of parameters like device gate length (Lg), extended source length and height, SiGe mole fraction (x), oxide thickness (tox), gate dielectric material, and frequency (f). Furthermore, the influence of variation of dimensionality and material parameters in presence of noise on Drain Current Noise Power Spectral Density (Sid) and Gate Voltage Electron Noise Power Spectral Density (Svgee) are studied for different trap charge conditions. Assuming Gaussian distribution of trap charges at the interface, it is perceived that the effect of noise is more as compared to the case of absence of trap charges. In reference to other FET devices, present paper reports that, the proposed SG-ESTFET device under absence of trap charges, illustrates an improved Sid and Svgee value of 1.4 × 10−29 A2/Hz and 5.21 × 10−16 V2/Hz, respectively whereas under the presence of trap charges, Sid and Svgee value are 6.6 × 10−26 A2/Hz and 8.74 × 10−12 V2/Hz, respectively. Moreover, this study also reports that the generation recombination (G-R) noise is mainly prevailing at low and mid-frequencies in presence of trap charges while diffusion noise is prevailing at high-frequencies. Likewise, the flicker noise is observed to be noteworthy at low and medium-frequencies in absence of trap charges.

Low frequency noise in double heterostructure P-InAsSbP/n-InAs mid-IR photodiodes at cryogenic temperature: Photovoltaic mode and forward bias

Low frequency photocurrent noise, as well as the forward current noise are studied for the first time in mid-infrared InAsSbP/InAs double heterostructure photodiodes at 100 K. Two types of photodiodes are identified. For the first type, the spectral noise density, SI, depends on frequency as 1/fγ. For the second type, generation-recombination (GR) noise component dominates. Our results show that in those samples, it is one and the same local center that is responsible for the noise over the entire photocurrent range. The forward current noise in all samples is lower than that previously observed in InAsSbP/InAs single heterostructure photodiodes at 77 K. In samples demonstrating 1/fγ noise, the spectral noise density, SI, is proportional to the square of the current. In samples with GR noise, we also observe SI ~ I2 dependences in a certain current range. At higher currents, the noise decreases or tends to saturate. We show that at 100 K, the Nyquist noise is dominant and can be used for estimating the specific detectivity at photocurrents Iph ≤ 5·10−9 A for samples showing 1/fγ. noise, and at Iph ≤ 2·10−9 A for samples presenting GR noise component. At higher Iph the photocurrent noise should be also taken into account.

Investigation of 1/f and Lorentzian Noise in TMAH-treated Normally-Off GaN MISFETs

A tetramethyl ammonium hydroxide (TMAH)-treated normally-off Gallum nitride (GaN) metal-insulator-semiconductor field-effect transistor (MISFET) was fabricated and characterized using low-frequency noise (LFN) measurements in order to find the conduction mechanism and analyze the trapping behavior into the gate insulator as well as the GaN buffer layer. At the on-state, the noise spectra in the fabricated GaN device were 1/fγ properties with γ ≈ 1, which is explained by correlated mobility fluctuations (CMF). On the other hand, the device exhibited Lorentzian or generation-recombination (g-r) noises at the off-state due to deep-level trapping/de-trapping into the GaN buffer layer. The trap time constants (τi) calculated from the g-r noises became longer when the drain voltage increased up to 5 V, which was attributed to deep-level traps rather than shallow traps. The severe drain lag was also investigated from pulsed I-V measurement, which is supported by the noise behavior observed at the off-state.

Effect of Interface Traps on the RTS Noise Behavior of Junctionless Nanowires

This work presents a study on the effects of single interface traps throughout the Junctionless Nanowire Transistor (JNT). The results are obtained by analyzing the Random Telegraph Signal noise of the device, which consists of an exception of the generation-recombination noise. The results obtained are mostly from numerical simulation, validated through experimental data. As in physical devices, it is impossible to obtain a single trap in specific locations, we have used a distribution of traps with similar characteristics in a way that they behave like a single trap. The results show the behave considering a set of traps distributions, using an exponential model. The traps are distributed from the conduction band to the valence band.
 Keywords– JNT; RTS Noise; G-r Noise; Interface Traps.

Thermal kinetic inductance detectors for millimeter-wave detection

Thermal Kinetic-Inductance Detectors (TKIDs) combine the excellent noise performance of traditional bolometers with a radio frequency multiplexing architecture that enables the large detector counts needed for the next generation of millimeter-wave instruments. In this paper, we first discuss the expected noise sources in TKIDs and derive the limits where the phonon noise contribution dominates over the other detector noise terms: generation–recombination, amplifier, and two-level system noise. Second, we characterize aluminum TKIDs in a dark environment. We present measurements of TKID resonators with quality factors of about 105 at 80 mK. We also discuss the bolometer thermal conductance, heat capacity, and time constants. These were measured by the use of a resistor on the thermal island to excite the bolometers. These dark aluminum TKIDs demonstrate a noise equivalent power, NEP = 2×10−17W/Hz, with a 1/f knee at 0.1 Hz, which provides background noise limited performance for ground-based telescopes observing at 150 GHz.

Low frequency noise-dark current correlations in HgCdTe infrared photodetectors.

In this paper, low frequency noise and dark current correlation is investigated as a function of reverse bias and temperature for short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) HgCdTe homo-junction photodetectors. Modelling of dark current-voltage characteristics shows that the detectors have ohmic-behavior under small reverse bias, thus enabling further analysis of 1/f noise-current dependences with the empirical square-law relation (SI ∼ I2) at different temperature regions. It is found that for the SWIR and MWIR devices, the total 1/f noise spectral density at arbitrary temperatures can be modelled by the sum of shunt and generation-recombination noise as SI(T,f)=[αSHISH2(T)+αG-RIG-R2(T)]/f, with no contribution from the diffusion component observed. On the other hand, for the LWIR device the diffusion component induced 1/f noise that cannot be overlooked in high temperature regions, and a 1/f noise-current correlation of SI(T,f)={αs[IDIFF2(T)+IG-R2(T)]+αSHISH2(T)}/f is proposed, with a shared noise coefficient of αs ≅ 1 × 10-9 which is close to that calculated for shunt noise. The 1/f noise-current correlation established in this work can provide a powerful tool to study the low frequency noise characteristics in HgCdTe-based photodetectors and to help optimizing the "true" detectivity of devices operating at low frequency regime.

An analysis of carrier dynamics in methylammonium lead triiodide perovskite solar cells using cross correlation noise spectroscopy

Using cross correlation current noise spectroscopy, we have investigated carrier dynamics in methylammonium lead triiodide solar cells. This method provides space selectivity for devices with a planar multi-layered structure, effectively amplifying current noise contributions coming from the most resistive element of the stack. In the studied solar cells, we observe near full-scale shot noise, indicating the dominance of noise generation by a single source, likely the interface between the perovskite and the spiro-organic 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene hole-transport layer. We argue that the strong 1/f noise term has contributions from both the perovskite layer and interfaces. It displays a non-ideal dependence on photocurrent, S∝I1.4 (instead of usual S∝I2), which is likely due to current-induced halide migration. Finally, we observe generation–recombination noise. We argue that this contribution is due to bimolecular recombination in the perovskite bulk absorption layer. Extrapolating our results, we estimate that at standard 1 sun illumination, the electron–hole recombination time is 5 μs.

Effect of Gate Structure on the Trapping Behavior of GaN Junctionless FinFETs

We investigated the performances of GaN junctionless fin-shaped field-effect transistors (FinFETs) with two different types of gate structures; overlapped- and partially covered-gate. DC, low-frequency noise (LFN), and pulsed I-V characterization measurements were performed and analyzed together in order to identify the conduction mechanism and examine both the interface and buffer traps in the devices. The fabricated GaN junctionless device with overlapped-gate structure exhibits improved DC and noise performance compared to the device with partially covered-gate, even though its gate length is much larger. The LFN behavior was found to be dominated by carrier number fluctuations (CNF). At off-state, the device with partially covered-gate exhibits generation-recombination (g-r) noise on top of 1/ ${f}$ noise. This superposition is correlated with the severe current collapse revealed by pulsed I-V measurements. In contrast, the device with overlapped-gate shows clear 1/ ${f}$ behavior without g-r noise.

Discussion on the Figures of Merit of Identified Traps Located in the Si Film: Surface Versus Volume Trap Densities

In this work a discussion on the estimated volume trap densities (NT) compared to surface traps densities (Neff) related to identified traps in the Si fin of Si/SiGe superlattice I/O n-channel FinFETs using low frequency noise spectroscopy is made. The investigated devices present a fin width of 10 nm, a fin height of 10 nm and four fins in parallel, leading to an equivalent channel width of 120 nm. The equivalent oxide thickness (EOT) is 5.6 nm. More details on the device fabrication and experimental setup may be found in [1,2]. The noise spectra and the estimated surface traps densities are provided in [3]. In this work, focus is only on the identified T4 trap, for which using the linear dependence that should exist between A0i and t0i related to the same trap, without any other assumption, a surface trap density of 2.8∙1012cm-2 is obtained [3]. It should be noted that from the 1/f flat-band noise level an interface trap density value of about 1.9∙1018 eV-1cm-3 is obtained at 300 K.However, as the traps in the Si film are related to a volume phenomenon, two methodologies to estimate the volume trap densities are employed: one using the relationship between the surface trap density and volume trap densitiy [4], where B is a coefficient estimated to be 1/3 [4,5]; and a second one from the temperature (T) evolution at fixed frequency of the Lorentzian plateau level associated to the same trap (from equation 34 in [4]). Using the first method leads to a volume trap density of T4 of about 1.7∙1019 cm-3.The second method consists to use the maximum of the measured Svg_Lor(f 0,T) dependence with temperature. Indeed, the Svg_Lor(f 0,T) of Lorentzians associated to the same trap are proportional with ti(T)/{1 + [2pf 0ti(T)]2}. For a given frequency f 0, if 2pf 0ti(T) ≫ 1, SVg_Lor(f 0,T) ∝ ti(T)]-1, and SVg_Lor(f 0,T) increases with increasing temperature because ti decreases. If 2pf 0ti(T) ≪ 1, then SVg_Lor(f 0,T) ∝ ti(T) and SVg_Lor(f 0,T) decreases with increasing temperature, as explained in detail in [4]. The evolution of the Svg_Lor(f 0,T)∙f 0 in a temperature range where T4 traps are active is illustrated in Figure 1 and presents a bell-shaped behavior, as expected. Using this method, volume trap densities of about 1.25∙1018 cm-3 for f 0 = 10 kHz and of about 1.1∙1018 cm-3 for f 0 = 14 kHz are obtained. It may be observed that the estimated volume trap densities of the T4 defect are about one decade lower than when using the first method. This overestimation by the first method is related to the fact that the theoretical B coefficient was determined for conventional planar devices with one gate [4,5]. Moreover, it may be noticed that the second method is dependent on the fixed f 0 selected.The paper will present a discussion with more details, considering all identified traps in [1] and considering additional new low frequency noise spectroscopy results.References :[1] Hellings, H. Mertens, A. Subirats, E. Simoen, T. Schram, L.-A. Ragnarsson et al., “Si/SiGe superlattice I/O finFETs in a vertically-stacked Gate-All-Around horizontal Nanowire Technology”, in Tech. Dig. Symp. on VLSI Technology, The IEEE New York, 2018, p.p. 85-86, DOI: 10.1109/VLSIT.2018.8510654.[2] Boudier, B. Cretu, E. Simoen, R. Carin, A. Veloso, N. Collaert, and A. Thean, “Low frequency noise assessment in n- and p-channel sub-10 nm triple-gate FinFETs: Part I: Theory and methodology,” Solid State Electron., vol. 128, pp. 102-108, 2017, DOI: 10.1016/j.sse.2016.10.012.[3] Boudier, B. Cretu, E. Simoen, G. Hellings, T. Schram, H. Mertens and D. Linten, “Low frequency noise analysis on Si/SiGe superlattice I/O n-channel FinFETs”, In Proceedings of EUROSOI-ULIS’2019.[4] Lukyanchikova, “Noise and Fluctuations Control in Electronic Device”, edited by A. Balandin, American Scientific, Riverside, CA, 2002, pp. 201-233.[5] Yau and C-T. Sah, “Theory and experiments of low-frequency generation-recombination noise in MOS transistors”, IEEE Trans. Electron Dev., 1969, vol.16, pp. 170-177.Figure 1 : SVg_Lor(f 0,T)·f 0 versus temperature for the T4 trap identified in [3]; on the secondary Oy axis the characteristic frequency f 0i of the Lorentzians is displayed in function of temperature. Figure 1

Deep insight into material-dependent DC performance of Fe DS-SBTFET and its noise analysis in the presence of interface traps

This paper reports the DC performance of Ferroelectric Dopant Segregated Schottky Barrier TFET (Fe DS-SBTFET) for different types of materials in the Dopant Segregated (DS) layer and its noise analysis considering the presence of Gaussian and uniform interface traps with the device being subjected to variation in ferroelectric thickness. Silicon doped HfO2 ferroelectric layer increases the tunneling junction electric field. Maximum ION/IOFF ratio of 1.2 × 109 and 14 mV/dec Subthreshold Swing (SS) have been achieved by using ferroelectric layer of thickness 6 nm. Different electrical parameters such as SS and ION/IOFF ratio have been explored for various trap concentrations. ON state current deteriorates with the increase in trap concentration. The dominancy of different noise components has been analysed with respect to frequency. Both flicker noise and generation-recombination noise contribute to the net noise at low frequency range. Flicker noise dominates at mid frequency and the major contribution at high frequency is of diffusion noise.