Carrier Injection Effect Research Articles

Modeling of HCI effect in nFinFET for circuit reliability simulation

This paper proposes an equivalent circuit model for simulating the Hot Carrier Injection (HCI) effect. This model is developed based on the N-FinFET in the 12 nm Process Design Kit (PDK) and incorporates arithmetic units and electrical components from the Electronic Design Automatic (EDA) software. Input parameters can be freely modified by the user, such as stress time, ambient temperature, gate length, gate width and process corner. The model also considers the influence of the voltage at each end of the transistor on the HCI effect. The model can be accessed in the EDA tool just like a normal transistor and can be used to evaluate the HCI effect on circuits without modifying the SPICE model. The accuracy and applicability of this model has been verified by comparing it with measured results from other published literature.

Effects of athermal carrier injection on Co-60 gamma-ray damage in SiC merged-PiN Schottky diodes

Co-60 gamma irradiation of SiC merged-PiN Schottky (MPS) diodes up to fluences of 1 Mrad (Si) produces increases in both forward and reverse current, with less damage when the devices are biased during irradiation. Subsequent injection of minority carriers by forward biasing at 300 K can partially produce some damage recovery, but at high forward biases also can lead to further degradation of the devices, even in the absence of radiation damage. Recombination-enhanced annealing by carrier injection overall is not an effective technique for recovering gamma-induced damage in SiC MPS diodes, especially when compared to other near athermal methods like electron wind force annealing.

Effect of non-uniform carrier injection on two-state lasing in quantum dot microdisks with split electrical contact

In this papaer, the emission characteristics of InAs/InGaAs quantum dot (QD) microdisk lasers, of different cavity diameters, with a top split electrical contact formed using the focused ion beam technique are investigated. The dependences of the threshold currents of two-state lasing (i.e. currents corresponding to the start of the ground- and excited-state lasing) for microdisks of 24 and 28 μm diameters on the electrical contact area are presented. The contact area was found to influence the threshold currents of two-state lasing in microdisks. It is shown that a decrease in the area of the injected electrical contact leads to a decrease in the current corresponding to the start of the excited-state lasing, while the ground-state (GS) lasing threshold remains virtually unchanged. The temperature evolution of the threshold currents for two-state lasing was also studied in microdisks with different electrical contact areas. We demonstrate that the use of contacts of different areas is a method of controlling the threshold currents of two-state lasing and can be used in engineering of QD lasers intended, for example, for multi-level signal transmission with wavelength multiplexing by switching from the GS to excited-state lasing.

Semiconductor–Semimetal Composite Engineering Enabling Record‐High Thermoelectric Power Density for Low‐Temperature Energy Harvesting

AbstractSustained thermoelectric efforts have concentrated on the enhancement of conversion efficiency of power generators, while simultaneously achieving high output power continues to lag. Specifically, the highest output power density of emerging Mg‐based modules reported so far is only half of that of commercial Bi2Te3‐based, mainly due to the low power factor of MgAgSb. Herein, homogenously distributed MgCuSb in situ nanoprecipitates in the MgAgSb matrix effectively optimized carrier concentration due to the effect of carrier injection from the metal–semiconductor Ohmic contact. As a result, a record‐high average power factor of 27.2 µW cm−1 K−2 is obtained in MgCu0.1Ag0.87Sb0.99 composite within the temperature range of 300–550 K, which is much higher than ever reported values of MgAgSb system. Benefiting from the combination of the optimized average power factor of p‐leg and low interface resistivity, a fabricated eight‐pair MgCu0.1Ag0.87Sb0.99/Mg3.2Bi1.5Sb0.5 module demonstrates an unprecedently high output power density of 2.9 W cm−2 under a temperature difference of 300 K, outperforming all low‐temperature advanced thermoelectric modules. Meanwhile, a competitive conversion efficiency of 7.65% is obtained simultaneously. The work significantly advances high‐power thermoelectric applications of Mg‐based modules in the field of low‐temperature sustainable energy harvesting.

Surface doping effect on the optoelectronic performance of 2D organic crystals based on cyano-substituted perylene diimides

Compared to organic thin films, organic single crystals offer significant potential in organic phototransistors (OPTs) due to their enhanced charge transport, large surface area, and defect-free nature. However, the development of n-type semiconductors has lagged behind p-type semiconductors. To enhance semiconductor device performance, a doping process can be employed, which typically involves the introduction of charged impurities into the crystalline semiconducting material. Its aim is to reduce the Ohmic losses, increase carrier density, improve transport capabilities, and facilitate effective carrier injection, ultimately enhancing the electrical properties of the material. Traditional doping processes, however, often pose a risk of damaging the structure of single crystals. In this study, we have synthesized novel cyano-substituted chiral perylene diimides, which self-assemble into two-dimensional single crystals that can be used for n-type semiconductor devices. We have employed a surface doping strategy using diethylamine vapor without disrupting the crystal structure. The fabricated devices exhibit significantly higher charge transport properties after doping, achieving a maximum electron mobility of 0.14 cm² V−¹ s−¹, representing an improvement of over threefold. Furthermore, the optoelectronic performance of the doped devices has significantly improved, with the external quantum efficiency increased by over 9 times and the significantly improved response time. These results suggest that our surface doping technology is a promising way for enhancing the performance of 2D organic single-crystal OPTs.

Acid-base engineered strategy of HKUST-1 dopants for high electrical conductivity of single-walled carbon nanotubes films

The improvement of electrical conductivity of carbon nanotubes is still a challenge via tuning the carrier concentration and mobility with organic or inorganic dopants due to low doping efficiency. In this paper, single-walled carbon nanotubes (SWCNTs) have been doped with Cu3(BTC)2·(H2O)3 (HKUST-1) as metal organic frameworks via simple mixing and vacuum filtration method. With fine acid or base post-treatment, the crystal structure of HKUST-1 was broken into fragments with more active sites and provided plenty of carriers injecting into SWCNTs. The electrical conductivity of SWCNTs/HKUST-1 films was increased by almost 2.5 times compared to pristine SWCNTs at room temperature. The defect tuning of dopants on SWCNTs surface is an effective carrier injection strategy, which provides a way to improve the electrical conductivity of SWCNTs.

A HCI-hardened self-healing operational amplifier circuit

In this paper, a self-healing operational amplifier circuit to deal with hot carrier injection (HCI) effect is proposed. An inverter-based operational amplifier is implemented. The influence degree of HCI effect to performance of the operational amplifier is studied which utilizes an equivalent circuit model of HCI effect. A monitoring circuit is proposed to monitor the degree of HCI degradation. A charge pump circuit is utilized to generate a corresponding voltage according to the result of monitoring circuit. The output voltage of the charge pump circuit is feedback to tune the substrate voltage of the operational amplifier (and the monitoring circuit) to mitigate degradation. The simulation results show that the self-healing operational amplifier can maintain the performance at low temperature and room temperature for 50 years (and high temperature for 30 year) under HCI effect. The gain of the inverter-based operational amplifier without self-healing is reduced from 45 dB to 9.6 dB after 50 years, and the gain of the self-healing operational amplifier will maintain at about 46 dB among 50 years. The influence of HCI effect on bandwidth and phase margin is less than that of temperature and process corner. The lifetime of self-healing operational amplifier circuit is >5 times longer than lifetime of based on inverter operational amplifier circuit without self-healing. In addition, the self-healing operational amplifier is robust to process corner.

Synergistic Effect of Chiral Metasurface and Hot Carrier Injection Enabling Manipulation of Valley Polarization of WSe2 at Room Temperature

AbstractThe unique band structure of monolayer transition metal dichalcogenides (TMDC) provides an important platform for spintronic and valleytronic devices. Various approaches, such as in‐plane electric field and out‐of‐plane magnetic field, have been proposed to actively control the valley polarization. In this work, we propose a synergistic effect involving chiral near‐field interactions and hot carrier injection to actively control the valley polarization emission of WSe2 at room temperature (RT). The degree of valley polarization is enhanced from near zero (for pure WSe2) to 20% under non‐resonant optical excitation (532 nm) when monolayer WSe2 is coupled with the chiral near field of plasmonic metasurface. More importantly, the application of near‐infrared light (wavelength of 970 to 1600 nm) illumination further enhances the valley polarization from 20% to 30%, which is attributed to plasmonic‐induced hot carrier injection from the metasurface to WSe2. The synergistic effect of the chiral near field and infrared light pumping offers another strategy to manipulate the valley polarization emission in monolayer TMDs at room temperature, paving the way for future applications of opto‐valleytronic/spintronic devices based on these 2D materials.

Injection-limited and space-charge-limited conduction in wide bandgap semiconductors with velocity saturation effect

Carrier conduction in wide bandgap semiconductors (WBS) often exhibits velocity saturation at the high-electric field regime. How such effects influence the transition between contact-limited and space-charge-limited current (SCLC) in a two-terminal device remains largely unexplored thus far. Here, we develop a generalized carrier transport model that includes contact-limited field-induced carrier injection, space charge, carrier scattering, and velocity saturation effect. The model reveals various transitional behaviors in the current–voltage characteristics, encompassing Fowler–Nordheim emission, trap-free Mott–Gurney (MG) SCLC, and velocity-saturated SCLC. Using GaN, 6H–SiC and 4H–SiC WBS as examples, we show that the velocity-saturated SCLC completely dominates the high-voltage (102–104 V) transport for typical sub-μm GaN and SiC diodes, thus unraveling velocity-saturated SCLC as a central transport mechanism in WBG electronics.

A HCI self-healing circuit of a bandgap reference circuit with curvature compensation

In this paper, the performance degradation of a bandgap reference circuit with curvature compensation under the hot carrier injection (HCI) effect is studied, and a self-healing circuit is proposed. The intrinsic performance of the curvature compensation bandgap circuit achieved a temperature coefficient (TC) of 1.949 ppm/°C and an output reference voltage of 384.748 mV under a 1.2 V power supply voltage between −40 °C to 125 °C. The TC of the reference circuit will increase to 8.033 ppm/°C and the output reference voltage decreases to 384.318 mV after 50 years under the HCI effect. The study found that the gain decrease of the op-amp in the reference circuit leads to a decrease in the output voltage, and the decrease of the compensation current in the curvature compensation circuit leads to the degradation of the TC. A self-healing circuit is designed to mitigate the impact of the HCI effect. The simulation results show that the TC of the self-healing reference circuit is 3.934 ppm/°C and the output reference voltage is 384.655 mV after 50 years under the HCI effect.

Transient photocurrent and optical absorption of disordered thin-film semiconductors: In-depth injection and nonlinear response.

The time-of-flight method is a fundamental approach for characterizing the transport properties of semiconductors. Recently, the transient photocurrent and optical absorption kinetics have been simultaneously measured for thin films; pulsed-light excitation of thin films should give rise to non-negligible in-depth carrier injection. Yet, the effects of in-depth carrier injection on the transient currents and optical absorption have not yet been elucidated theoretically. Here, by considering the in-depth carrier injection in simulations, we found a 1/t1-α/2 initial time (t) dependence rather than the conventional 1/t1-α dependence under a weak external electric field, where α < 1 is the index of dispersive diffusion. The asymptotic transient currents are not influenced by the initial in-depth carrier injection and follow the conventional 1/t1+α time dependence. We also present the relation between the field-dependent mobility coefficient and the diffusion coefficient when the transport is dispersive. The field dependence of the transport coefficients influences the transit time in the photocurrent kinetics dividing two power-law decay regimes. The classical Scher-Montroll theory predicts that a1 + a2 = 2 when the initial photocurrent decay is given by 1/ta1 and the asymptotic photocurrent decay is given by 1/ta2 . The results shed light on the interpretation of the power-law exponent of 1/ta1 when a1 + a2 ≠ 2.

Milliwatt-power sub-230-nm AlGaN LEDs with &amp;gt;1500 h lifetime on a single-crystal AlN substrate with many quantum wells for effective carrier injection

We fabricated sub-230-nm (far UV-C) light emitting diodes (LEDs) on a single-crystal AlN substrate. With 20 quantum well cycles implemented to enhance carrier injection into the active layers, over 1-mW output power (1.4 and 3.1 mW for 226- and 229-nm LEDs, respectively) was obtained under 100-mA operation. The maximum output power reached 21.1 mW for the single-chip 229-nm LED operating at 700 mA, without significant drooping. The forward voltage for both sub-230-nm LEDs operating at 100 mA was low (5.9 V) due to their low resistances and ideal Ohmic contacts between metal and semiconductor components. Additionally, wall plug efficiencies were 0.24% and 0.53% for the 226- and 229-nm LEDs, respectively. The lifetime of the 226-nm LED while operating at 25 °C reached over 1500 h and did not show current leakage, even after 1524 h. This long lifetime will be achieved by improving carrier injection due to many quantum wells, using a high-quality AlN substrate and achieving high wall plug efficiency.

Investigation on carrier injection tailoring and electroluminescence of WSe2 quantum dots in light-emitting diodes

WSe2 quantum dots (QDs) with exceptional properties are facilely synthesized with liquid phase exfoliation and hydrothermal reaction, and characterized with scanning electron microscope, atomic force microscope, transmission electron microscope and X-ray photoelectron spectroscopy. The WSe2 QDs show good film morphology and effective carrier injection tailoring. Using 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as emitter, the near ultraviolet organic light-emitting diodes (NUV OLEDs) show maximum radiance of 1.25 mW/cm2 and external quantum efficiency (EQE) of 0.48% in inverted device with WSe2 QDs tailoring electron injection. The corresponding normal UV OLEDs show maximum radiance of 1.82 mW/cm2 and EQE of 1.39% with WSe2 QDs tailoring hole injection. Impedance spectroscopy analysis clarifies carrier injection tunability of WSe2 QDs. LEDs using WSe2 QDs as emitter are pioneeringly fabricated, showing maximum luminance of 426 cd/m2, EQE of 0.39%, luminous efficiency of 0.3 cd/A, power efficiency of 0.13 lm/W, and voltage dependent electroluminescent spectra. Ours results pave an alternative approach for interface modification, developing novel WSe2 QDs emitters, and boosting WSe2 QDs applications.

An equivalent circuit model of HCI effect for short-channel N-MOSFET

The hot carrier injection (HCI) effect is an essential factor for the reliability of N-MOSFET. Under long-term usage time, the HCI effect will affect the threshold voltage, transconductance, saturation drain-source current of N-MOSFET, etc. It will seriously affect the performance and lifetime of products. The current model for HCI effect simulation is mainly by modifying the SPICE model of N-MOSFET, which requires complex experiments and parameter extraction. This paper establishes an HCI effect equivalent circuit model for a 65 nm N-MOSFET. Based on the N-MOSFET model in a 65 nm Process Design Kit (PDK), essential electrical components and arithmetic components (which are provided by EDA tools), this equivalent circuit model achieves the HCI effect simulation. This equivalent circuit model offers five tunable input parameters for the user, which are channel width (W), channel length (L), ambient temperature (Temp), stress time (Year), process corner (fast, typical, slow). The effect of gate-source voltage, drain-source voltage, and gate-drain voltage on HCI effect is included in this model. The simulation results of this model are compared with the measured results in other literatures, and the results are fitted well.

14‐3: Extremely Short‐Channel LTPS TFT Technologies for High‐Performance Low‐Power, and Reliable AMOLED displays

This paper presents recent progress to scale down low‐temperature polysilicon (LTPS) TFT technologies in the extremely short‐channel length regime for AMOLED displays. Process integration of short‐channel gate and narrow‐width polysilicon into scaled equivalent gate‐oxide thickness (EOT), is explored, in conjunction with enhanced poly crystallization by reducing defect density‐of‐state (DOS) especially in the grain boundaries of the channel region. We obtain more than twice higher current drive (Ion) with significantly‐reduced parasitic gate capacitance, thereby enabling high‐performance high‐frequency panel operations. In addition to superior panel performance in scaled LTPS TFTs, reliable devices are attained, demonstrating robust device characteristics for negative‐bias instability (NBTI) and hot carrier injection (HCI) effects. Physics‐based analysis, based on experimental data and numerical device simulations, is performed to gain more insight in the TFT technologies.

Unraveling the Origin of Dark Current in Organic Bulk Heterojunction Photodiodes for Achieving High Near-Infrared Detectivity

Organic infrared materials are attractive due to their high absorption coefficients and facile tuning of the absorption spectrum beyond that of silicon. Although bulk heterojunctions (BHJs) are widely used in organic photodetectors (OPDs), achieving a high signal-to-noise ratio in the near-infrared spectrum is often challenging due to the inherently large dark currents in low-bandgap polymers and their blending morphology effect. Herein, we investigate the origin of dark currents in near-infrared OPDs and reveal a strategy to improve the detectivity in terms of two aspects: (1) donor–acceptor blending morphology and (2) effects of carrier injection from outer electrodes. To do so, a series of random terpolymers were synthesized in a similar band structure and their blending morphology with the PC71BM acceptor was gradually controlled. As the phase separation was smaller, the dark current gradually reduced while the responsivity increased, leading to a higher detectivity. Complex charge-transporting paths formed under the fine percolating network account for the dark current reduction, while the increased heterojunction area facilitates the dissociation of the photogenerated excitons. From our thermal admittance spectroscopy, deeper sub-bandgap states were found under the smaller phase separation, further contributing to the dark current reduction. Second, the carrier injection effect was revealed by inserting a charge-blocking layer at the active layer/electrode interface. While manipulating both parameters could yield a high near-infrared detectivity up to 1012 Jones at −0.5 V, the blending morphology effect turns out to be more dominant over the carrier injection effect in suppressing the dark current and achieving higher detectivity in BHJ OPDs.

Carrier Injection to In0.4Ga0.6As/GaAs Surface Quantum Dots in Coupled Hybrid Nanostructures

Stacking growth of the InGaAs quantum dots (QDs) on top of a carrier injection layer is a very useful strategy to develop QD devices. This research aims to study the carrier injection effect in hybrid structures with a layer of In0.4Ga0.6As surface quantum dots (SQDs), coupled to an injection layer of either one layer of In0.4Ga0.6As buried QDs (BQDs) or an In0.15Ga0.85As quantum well (QW), both through a 10 nm GaAs thin spacer. Spectroscopic measurements show that carrier capture and emission efficiency for SQDs in the BQD injection structure is better than that of the QW injection, due to strong physical and electrical coupling between the two QD layers. In the case of QW injection, although most carriers can be collected into the QW, they then tunnel into the wetting layer of the SQDs and are subsequently lost to surface states via non-radiative recombination. Therefore, the QW as an injection source for SQDs may not work as well as the BQDs for stacking coupled SQDs structures.

Mechanism of Non-Ideal Transfer Characteristic at Low Drain Voltage in Metal-Capped Amorphous Oxide Thin Film Transistor

Issues of amorphous oxide semiconductors (AOSs) thin-film transistors (TFTs) mainly focus on improving electrical performance and stability. Currently, the hump, the abnormal transfer characteristic, is also an essential factor of AOSs TFT. The hump phenomenon was observed for AOS-TFTs with a metal capping (MC) layer under various measurement conditions. The mobility in the MC TFT was improved from 14.8 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs to 19.2 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs compared to that of the conventional TFTs. The improved electrical characteristics in the MC structure are representative of the carrier injection effect and the change of the current path. This reason reveals that the MC structure has a hump phenomenon under the low drain to source voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{DS}$ </tex-math></inline-formula> ). The hump characteristic does not significantly affect the overall MC TFT characteristics (transfer characteristic, improved electrical characteristics through MC structure, etc.). In addition, it was confirmed that it exhibits very stable hump characteristics through repeated measurements and uniformity. It was found that two current paths are formed mainly due to carrier injection from the metal capping layer in the hump phenomenon observed at low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{DS}$ </tex-math></inline-formula> . These divided current paths can lead to two on-currents ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{on}$ </tex-math></inline-formula> ) in the transfer curve. Many studies have recently been conducted to fabricate semiconductor devices with multi-values such as 0, 1, and 2. This divided current path could propose a simple method to achieve multi-values with an easy process.

Modeling the Charge State of Monatomic Hydrogen and Other Defects with Arbitrary Concentrations in Crystalline Silicon

A rigorous physical‐mathematical model for predicting the charge states of both mono‐ and multivalent defects with arbitrary concentrations in Si in both thermal equilibrium and non‐equilibrium steady‐state conditions is presented. The model avoids the assumption that the defect concentration is much lower than the doping level, which is common in previous approaches. It is shown that the general occupancy ratio given by α = (kn1 + p)/(kn + p1) is still valid under these more general conditions. However, more caution needs to be taken when calculating the equilibrium and excess carrier densities in the presence of larger defect concentrations, because of: a) the non‐negligible contribution to n0 and p0 from defect ionisation, and b) unequal Δn and Δp caused by the change in the occupied states at the defect level from equilibrium to non‐equilibrium. Modeled examples of monatomic H and interstitial Fe in Si are shown and the effects of defect concentration, temperature, and carrier injection are discussed.

Multipoint Detection Technique with the Best Clock Signal Closed-Loop Feedback to Prolong FPGA Performance

The degradation effect of a field-programmable gate array becomes a significant issue due to the high density of logic circuits inside the field-programmable gate array. The degradation effect occurs because of the rapid technology scaling process of the field-programmable gate array while sustaining its performance. One parameter that causes the degradation effect is the delay occurrence caused by the hot carrier injection and negative bias temperature instability. As such, this research proposed a multipoint detection technique that detects the delay occurrence caused by the hot carrier injection and negative bias temperature instability degradation effects. The multipoint detection technique also assisted in signaling the aging effect on the field-programmable gate array caused by the delay occurrence. The multipoint detection technique was also integrated with a method to optimize the performance of the field-programmable gate array via an automatic clock correction scheme, which could provide the best clock signal for prolonging the field-programmable gate array performance that degraded due to the degradation effect. The delay degradation effect ranged from 0° to 360° phase shifts that happened in the field-programmable gate array as an input feeder into the multipoint detection technique. With the ability to provide closed-loop feedback, the proposed multipoint detection technique offered the best clock signal to prolong the field-programmable gate array performance. The results obtained using the multipoint detection technique could detect the remaining lifetime of the field-programmable gate array and propose the best possible signal to prolong the field-programmable gate array’s performance. The validation showed that the multipoint detection technique could prolong the performance of the degraded field-programmable gate array by 13.89%. With the improvement shown using the multipoint detection technique, it was shown that compensating for the degradation effect of the field-programmable gate array with the best clock signal prolonged the performances.