Effect Of Electron Injection Research Articles

Hot-carrier degradation in deep-submicrometer nMOSFETs: lightly doped drain vs. large angle tilt implanted drain

The hot-carrier degradation of lightly doped drain (LDD) and large angle tilt implanted drain (LATID) nMOSFETs of a 0.35 μm CMOS technology is analysed and compared by means of I–V characterisation and charge pumping current measurements. LATID nMOSFETs are found to exhibit a significant improvement in terms of both, current drivability and hot-carrier immunity at maximum substrate current condition. The different factors which can be responsible for this improved hot-carrier resistance are investigated. It is shown that this must be attributed to a reduction of the maximum lateral electric field along the channel, but not to a minor generation of physical damage for a given electric field or to a reduced I–V susceptibility to a given amount of generated damage. Further to this analysis, the hot-carrier degradation comparison between LDD and LATID devices is extended to the whole range of gate-stress regimes and the effects of short electron injection (SEI) and short hole injection (SHI) phases on hot-carrier-stressed devices are analysed. Apart from a significant improved resistance to hot-carrier effects registered for LATID devices, a similar behaviour is observed for the two types of architectures. In this way, SEI phases are found to be an efficient tool for revealing part of the damage generated in stresses at low gate voltages, whereas the performance of a first SHI phase after stress at high gate bias is found to result in a significant additional degradation of the devices. This enhanced degradation is attributed to a sudden interface states build-up occurring in both, LDD and LATID devices, near the Si/spacer interface only under the first hot-hole injection condition.

Experimental results from an Imarad 8×8 pixellated CZT detector

This paper reports experimental results obtained from an 8×8 pixellated CZT detector provided by Imarad Imaging Systems. Three arbitrarily selected pixels were independently tested using γ rays of different energies. The signals from an anode pixel and the cathode were read out simultaneously. From the observations of the pulse waveforms from both the anode pixel and the cathode, the electron-injection effect leading to electron–hole combination was not observed. The best energy resolution at 122 keV from the three pixels was 7.8, 6.6 and 9.4 keV, respectively, while resolution at 662 keV was 29.3, 11.8 and 26.5 keV, respectively. The electronic noise from the three pixels was similar (5 keV), so the variation in the best energy resolution indicates material nonuniformity in the detector. For the material underneath the three selected pixels, the mobility-lifetime product for electrons was measured to be 3.4, 2.4 and 1.8 ( ×10 −3 cm 2/ V ), respectively, and the resistivity was measured to be 8, 10 and 8.3 ( ×10 9 Ω cm ), respectively. The variation in these results also shows the material nonuniformity across the detector. In the test with 662 keV γ rays, the pulse-height ratio of the signals from the cathode and pixel can be used to infer the interaction depth of single-pixel events. Results and analyses are presented in this paper.

Electron injection effect on formation and decomposition of C–H complexes in C-doped GaAs Base of H +-implanted InGaP/GaAs HBTs

We observed the current gain and turn-on voltage variations in H +-implanted InGaP/GaAs heterojunction bipolar transistors with carbon-doped bases under high temperature current stresses. The variation occurs in two stages: the first stage is characterized by a current gain increase and a turn-on voltage decrease, and the second by a current gain decrease and a turn-on voltage increase. The first variation is attributed to a decrease of the hole concentration in the base, caused by the formation of C–H complexes in the base. The second variation arises from an increase of the hole concentration in the base, which is brought about by a decomposition of the C–H complexes. Hydrogen in the base is diffused from the H +-implanted region predominantly during the HBT fabrication process. Both the formation and the decomposition of C–H complexes are assisted by current injection. The formation of C–H complexes may be enhanced by the energy transfer from 2 electrons. The decomposition of C–H complexes is dominated by the capturing of single electrons. After the variation, hydrogen do not cause “essential” degradation. Consequently, the HBTs must be finally free from hydrogen.

Alq 3: ab initio calculations of its structural and electronic properties in neutral and charged states

A detailed density functional theory study is presented for the structural and electronic properties of Alq 3, one of the electroluminescent material most successfully used in organic light-emitting diodes. Both geometrical isomers are considered, and interesting discrepancies are found in their electronic behavior. Calculations are compared with available experimental data and with the results of semiempirical models as well. The effects of hole and electron injection are clarified, and trap energies for the negative charge carriers are estimated.

Electron Injection Effects in Electroluminescent Devices Using Polymer Blend Thin Films

AbstractIn this paper, we discuss the effects of electron injection on electroluminescence (EL) efficiency in single-layer EL devices using blends of poly(N-vinylcarbazole) (PVK) and poly(3-nbutyl- p-pyridyl vinylene) (Bu-PPyV). Pure Bu-PPyV thin films suffer from formation of excimers due to the strong interchain interaction. Diluting Bu-PPyV with the high-energy-gap and holetransporting polymer PVK suppresses excimer formation and substantially raises both photoluminescence (PL) and EL efficiencies. The emission color is converted from red to green, indicating a transition from excimer emission to monomer emission of Bu-PPyV. The electron injection and EL efficiency can be fluther improved by adding small-molecule oxadiazoles into the blends as electron-transport materials. In optimized devices, an external EL quantum efficiency (backside emission only) as high as 0.8% photon/electron and practical brightnesses of 100 cd/m2 and 1000 cd/m2 can be achieved at ∼9V and ∼13.5V, respectively.

A comparison of square, triangular, and sinusoidal waveforms used for avalanche electron injection in MOS structures

A comparative study of the effects of square, triangular and sinusoidal avalanche electron injection waveforms on metal-oxide-silicon (MOS) structures has been performed. Electron injection using a square wave yields the largest shift in flatband voltage of the MOS structure for a given injected electron fluence, while the triangular waveform produces the smallest shift. However, the magnitude of the increase in interface state density is similar for all three avalanche electron injection waveforms. Also, all three techniques yield a characteristic temperature of 5750 K for the injected electrons, indicating similar physical injection mechanisms. Square wave avalanche electron injection underestimates the total electron fluence because the current measurement circuit cannot respond to the initial current transient. This current transient also results in damage to the silicon dioxide at an applied electric field lower than the critical dielectric strength. Thus, a comparison of different avalanche electron injection data must specify, not only the input signal, but also the current measurement circuit used.

Effects of high field electron injection into the gate oxide of P-channel metal–oxide–semiconductor transistors

Electron injection at high field and moderate fluence into the gate oxide of P-channel metal–oxide–semiconductor transistors creates net positive charges and related interfacial states as it has often been reported. A threshold electric field at around 7.2 MV/cm is found for the generation of positive charges. For this same oxide field the interfacial state density increases abruptly. For an average oxide field in the 8–9-MV/cm range, the densities of positive charges and interfacial states increase linearly with the fluence for F<1016 e/cm2 and saturate for F≳1017 e/cm2. The positive charge density is more important near the channel edges. The interfacial state density seems to be homogeneously distributed along the channel. The density of electron traps is negligible for the studied dry gate oxide except in the overlaps above drain and source and in some cases near the channel edges. The negative space charge, resulting from electron trapping in these regions, reduces the length of the electron injection and in some cases the surface of the channel which contributes to the charge pumping current. Two types of relaxation have been observed.

Polarization of VDF-TrFE copolymer films at elevated temperature

The buildup of the polarization of VDF-TrFE copolymer films, at room temperature and after various thermal treatments, is studied using the PWP (pressure wave propagation) method. This method allows the nondestructive measurement of the homogeneity of the piezoelectric coefficient. The samples are polarized at 100 degrees C, and the influence of different thermal treatments before polarization, and of the insulator-electrode interfaces, are analyzed. The behavior of the copolymer is compared to that described previously for poling experiments made at room temperature. The effect of electron injection at the cathode by nonblocking electrodes is clearly shown.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Hot electron injection in InAlGaAs/InGaAs ballistic collection transistors

Hot electron transport in InAlGaAs/InGaAs ballistic collection transistors (BCTs) is simulated using a self-consistent Monte Carlo method. The authors analyse the effects of hot electron injection on the device performance of BCTs with various injection energies. The simulation has shown that the base and collector transit times in BCTs have conspicuous dependences on the energy of hot electrons in the base region.

High field phenomena in thin plasma nitrided SiO 2 films

The effects of high field tunnel electron injection on the electrical properties of Al - thin plasma nitrided SiO 2 films - Si (p-type) structures are studied. Under high field injection, it has been observed that electron trapping, positive charge generation near the Si-SiO 2 interface (slow states) and fast state generation at the Si-SiO 2 interface have taken place. After high temperature N 2 annealing, the nitridation induced electron trap density is considerably decreased. Furthermore, under high field injection the generation rate of both the slow states and the interface states and consequently, the degradation rate of the nitrided oxide films have been also decreased after annealing.

Oxide trapping under spatially variable oxide electric field in the metal-oxide-silicon structure

An improved trapping-detrapping model is presented describing the effect of electron injection into the oxide of metal-oxide-silicon devices. The model covers both hot-electron and tunneling injection. It takes into account the spatial variation of the oxide electric field due to the trapped charge as well as the effect of this variation on the trapping-detrapping processes. The calculated results agree well with previously reported experimental results such as the field-dependent steady-state flatband voltage and the trapped charge centroid.

Degradation of the electrical characteristics of the Si–SiO2 interface induced by electron injection

The effects of electron injection on the electrical characteristics of the Si–SiO2 interface have been studied on metal-oxide-semiconductor type structures incorporating very thin oxide films (≲200 Å). Electron current across the oxide is obtained by Fowler–Nordheim tunneling in Al:SiO2:Si structures or by enhanced Fowler–Nordheim tunneling in Al:Si-rich-SiO2:SiO2:Si devices. The changes induced by charge injection in these structures were monitored by measuring the 1-MHz and the quasistatic capacitance versus voltage characteristic curves. In both structures negative charge trapping in the oxide and positive charge accumulation were observed as well as generation of interface states at approximately 0.6 eV from the top of the Si valence band. However, in structures with Si-rich-SiO2 layers an anomalous peak in the quasistatic capacitance curves was observed to be induced by the injection of electrons. The role of the Si-rich-SiO2 layer in these phenomena is discussed.

Electron spin resonance study of interface states induced by electron injection in metal-oxide-semiconductor devices

We find that electrons emitted from silicon into the oxide of metal-oxide-silicon devices generate amphoteric trivalent silicon (Pb center) defects at the Si/SiO2 interface. The Pb centers are generated in numbers approximately equal to that of the electron injection induced interface states. The effects of electron injection are similar to those of ionizing radiation to the extent that in both cases Pb centers are generated at the Si/SiO2 interface. However, the effects are not identical; ionizing radiation creates another trivalent silicon defect, termed E′, in the oxide. We are unable to observe any E′ generation in oxides subjected to electron injection. There appears to be a strong correlation between the number of trapped electrons and the electron injection induced Pb center interface states; this observation suggests that the trapping of electrons in the bulk of the oxides is in some way related to the creation of the Pb center interface state defects. We find that dry oxides subjected to a deuterium/nitrogen anneal exhibit less electron trapping than otherwise identical oxides which have been subjected to a hydrogen/nitrogen anneal. This observation is consistent with the idea that a hydrogen bond breaking event may be involved in electron capture.

The dispersion and instability of the work function difference in MOS structures

We report the effect of electron injection and of some parameters of technological process on the interface barrier heights (Al-SiO 2, Si-SiO 2) and on the effective metal-semiconductor work function difference in MOS structures. Microscopic models which can explain observed variations of both barrier heights are proposed.

Reliability effects on MOS transistors due to hot-carrier injection

The high drain-effect transistor characteristic observed after hot-carrier injection and trapping in the oxide has been found to be due to the uneven trapped-carrier distribution near the drain, which causes the threshold voltage to vary as a function of drain voltage. A discussion of the role and effects of both electron and hole injection is presented. The nonlinear distribution of carriers trapped in the gate oxide is described. One result is that the nonuniform surface band bending causes the subthreshold leakage to be an exponential function of the drain voltage. The combined increase in threshold voltage, subthreshold leakage, and a decrease in subthreshold slope will translate into slower circuit speed and higher standby power dissipation [37] in CMOS circuits. An experimental model of the mean time to failure, for NMOS devices fabricated with two different source-drain diffusions, is also presented. For the first time, the model has been extended to include the channel-length dependence. The model assumes a reliability criterion of less than a 10-mV threshold-voltage shift in 100 000 h of operation. Experimental results and subsequent calculations show that for 350-Å gate-oxide devices at 5.0 V operation, 2.5 µm is the minimum electrical channel-length device which can be fabricated using a traditional source-drain process. Conversely, submicrometer electrical channel-length devices can be fabricated using an arsenic-phosphorous "graded" source-drain process, even at 5.5-V operation.

Reliability Effects on MOS Transistors Due to Hot-Carrier Injection

The high drain-effect transistor characteristic observed after hot-carrier injection and trapping in the oxide has been found to be due to the uneven trapped-carrier distribution near the drain, which causes the threshold voltage to vary as a function of drain voltage. A discussion of the role and effects of both electron and hole injection is presented. The nonlinear distribution of carriers trapped in the gate oxide is described. One result is that the nonuniform surface band bending causes the subthreshold leakage to be an exponential function of the drain voltage. The combined increase in threshold voltage, subthreshold leakage, and a decrease in subthreshold slope will translate into slower circuit speed and higher standby power dissipation [37] in CMOS circuits. An experimental model of the mean time to failure, for NMOS devices fabricated with two different source-drain diffusions, is also presented. For the first time, the model has been extended to include the channel-length dependence. The model assumes a reliability criterion of less than a 10-mV threshold-voltage shift in 100 000 h of operation. Experimental results and subsequent calculations show that for 350-/spl Aring/ gate-oxide devices at 5.0 V operation, 2.5 /spl mu/m is the minimum electrical channel-length device which can be fabricated using a traditional source-drain process. Conversely, submicrometer electrical channel-length devices can be fabricated using an arsenic-phosphorous graded source-drain process, even at 5.5-V operation.

A Comparison of Ionizing Radiation and Hot Electron Effects in MOS Structures

The authors use electron spin resonance to compare the effects of electron injection and gamma radiation on MOS devices. Electron injection is similar to ionizing radiation in that in both cases P /sub b/ centers are generated at the Si/SiO/sub 2/ interface. However, the effects are not identical; although ionizing radiation creates E' centers in the SiO/sub 2/, they are unable to observe any E' generation in oxides subjected to electron injection.

The Effect of Hot Electron Injection on Interface Charge Density at the Silicon to Silicon Dioxide Interface

The avalanche injection of hot electrons at the silicon to silicon dioxide interface causes an anomalous N‐shaped shift of flatband voltage in accordance with the injected charge density and generates an interface state with widely distributed time constants. To explain the N‐shaped behavior, we propose a model which assumes electron trapping in the silicon dioxide and the generation of the donor‐type interface state. It is also observed that the orientation of silicon substrate strongly affects the generated interface‐state density. The generated interface‐state density of a (100) capacitor has a value approximately half that of a (111) capacitor. The energy level of the generated interface state is distributed near the middle of the energy gap of silicon. The dominant electron capture cross sections are approximately for both (100) and (111) capacitors.

(Invited) Non-Thermal Carrier Generation in MOS Structures

Influence of generated carriers originated by hot electrons and radiations is described in MOS structures. A holding time degradation in a dynamic RAM is first presented with the two-step impact-ionization model, which is verified by a series of experiments. The impact ionization rate in the high electric field near the drain is also calculated by a two dimensional analysis, which leads to an accurate substrate current estimation. Effects of hot electron injection into the gate oxide, and of trapping are then studied utilizing a stacked gate MOS structure. From those results, design constraints in small geometry MOS LSI's are discussed.

Characteristics of P-I-N laser detectors: their dependence on wavelength and temperature

Wavelength and temperature-dependent characteristics of silicon P-I-N laser detectors are studied using the modified Baraff theory. Both the electron or hole injection effect and photogeneration effect are considered in the calculation of the power spectral density of multiplication noise and efficiencies. The results thus obtained are compared with previous papers where the photogeneration effect was neglected.