Effect Of Incomplete Ionization Research Articles

Space charge limited corrections to the power figure of merit for diamond

An interpretation of the unipolar figure of merit is formulated for wide bandgap (WBG) semiconductors based on the on-state specific resistance (RON,sp) derived from the space charge limited current–voltage relationship (Mott–Gurney square law). The limitations of the traditional Ohmic RON,sp for WBG semiconductors are discussed, particularly at low doping, while the accuracy of the Mott–Gurney based RON,sp is confirmed by Silvaco ATLAS drift–diffusion simulations of diamond Schottky pin diodes. The effects of incomplete ionization are considered as well.

Effects of incomplete ionization on forward current–voltage characteristics of p-type diamond Schottky barrier diodes based on numerical simulation

The forward current–voltage characteristics of p-type diamond pseudo-vertical Schottky barrier diodes are investigated via numerical simulation. Impact ionization decrease the hole concentration of the p− drift layer from 1015 to 1014 cm–3 at 300 K, thereby increasing the forward voltage drop and on-resistance. When we consider an incomplete ionization with increasing temperature, the increase in the hole concentration is more dominant than the enhanced phonon scattering, thereby resulting in an increasing forward current. We modified the Ohmic contact for both metallic conduction at the p+ layer and incomplete ionization at the p– drift layer. The Baliga figure-of-merit of the device with and without incomplete ionization is 25 and 192 MW cm−2, respectively. Incomplete ionization should be considered in the numerical study of diamond power devices.

Effect of electrolyte concentration on effective surface charge of colloidal particles

The effective surface charge of colloid particles is an important parameter that determines the colloidal properties. However, it is still unclear whether the solvent environment (such as the electrolyte concentration) can affect the effective surface charge. Due to complicated effects relevant to the effective surface charge, such as the exchange of dissociable ions between the electrolyte and surface groups of polystyrene particles, the coupling effect of incomplete ionization of the surface groups of the particles and the adsorption of ions by colloidal particles, etc., it is rather difficult to accurately measure the surface charge and understand the mechanism of charge variation with solvent environment. To solve this problem, we measure the conductivities of polystyrene colloidal particles of carboxyl groups and sulfonic acid groups at various particle number densities and HCl concentrations. Since the cations generated from the two kinds of particles and HCl solution are all H<sup>+</sup> cations, the surface charge can be obtained by the conductivity-number density method (migrant method), no matter whether the cation exchanges occur between ionized positive ions of the electrolyte and colloidal particles. Based on the experimental results, the influences of HCl concentration and particle number density on the surface charge of colloidal particles are detected, and the reasons of the influence are analyzed. It is found that the change of the surface charge of the particles of carboxyl group with HCl concentration is faster than that of sulfonic acid group with the HCl concentration. For the same electrolyte concentration, the effective surface charge of carboxyl modified colloidal particles is related to the particle number density, while the charge of sulfonic modified particles is not. Considering the fact that the sulfonic acid group and carboxyl group are strong and weak acid groups respectively, the ionization of H<sup>+</sup> cations of the two different groups have profound influences on the cation replacement process, and affect the trend of the curve of the conductivity-particle number density. This effect further results in different change tendencies of effective surface charge with HCl concentration and particle number density. According to the theoretical model as described in this study, all experimental results are well explained. The mechanisms described in this article will be useful for stating the influencing factors of the surface effective charge, and the application of the effective charge to different phenomena relating to interparticle interactions with different parameters of solutions.

Theoretical investigation of incomplete ionization of dopants effect on p+nn-n+ 4H-SiC IMPATT diode

The effect of incomplete ionization of dopants on p+nn-n+ 4H silicon carbide (4H-SiC) impact-ionization-avalanche-transit-time (IMPATT) diodes has been investigated. Breakdown voltage, avalanche region width, DC to RF conversion efficiency and RF output power of the 4H-SiC IMPATT device with incomplete and complete ionization are given at different temperatures. Theoretical analysis reveals that the influence of the incomplete ionization of dopants on the performance of the p+nn-n+ 4H-SiC IMPATT devices cannot be ignored.

The Effect of Incomplete Ionization on SiC Devices during High Speed Switching

SiC devices such as MOSFETs and SBDs reduce power loss in fast-switching condition as compared to Si devices. However, shallow and deep levels in SiC significantly affect dynamic characteristics of SiC devices. We already reported that high densities of deep levels were discovered in Al+-implanted samples other than the shallow Al acceptor level. In this work, we applied the deep level to the TCAD simulation, and examined the behavior of the carriers at high dV/dt conditions.

PC1Dmod 6.2 – Improved Simulation of c-Si Devices with Updates on Device Physics and User Interface

In this paper we present a new update to PC1Dmod, which extends the original PC1D program by implementing Fermi-Dirac statistics and a range of state-of-the-art models in order to improve the accuracy of c-Si device simulation. In PC1Dmod 6.2 the list of models is further expanded to include a parameterization of incomplete ionization of dopants (Altermatt et al., J. Appl. Phys.100, 113715, 2006), with parameters for phosphorus, boron, arsenic, gallium and aluminum. The results have been verified against a previous implementation of the model. We show that the inclusion of incomplete ionization is of particular importance for moderately doped surface regions with doping densities in the range ∼5 × 1017 to ∼5×1019 cm-3, resulting in a deviation of up to 15% in the simulated recombination current density and sheet resistance. The effect of incomplete ionization is also shown to be more pronounced in devices made from compensated Si material. Furthermore, the default solar spectrum has also been updated in PC1Dmod 6.2, taking advantage of the increased maximum file size to include a more realistic representation. The generation profiles calculated using PC1Dmod 6.2 together with input from OPAL 2 agree well with results from Sentaurus TCAD for both planar and pyramidally textured surfaces, thus facilitating a more direct comparison between PC1Dmod 6.2 and other simulation programs utilizing standard spectra. The simulation comparison is also extended to the electrical performance of the modeled devices, showing good agreement in the calculated short-circuit current density for a range of planar and textured solar cells with varying emitter doping. Finally, several new output options, including emitter saturation current and injection-dependent lifetime curves have been added, enabling a simpler and more direct way for users to access and plot important device properties.

Adapted parameterization of incomplete ionization in aluminum-doped silicon and impact on numerical device simulation

The amount of incomplete ionization of aluminum-doped silicon is measured at room temperature by comparing electrochemical capacitance-voltage measurements with micro Raman spectroscopy. It is shown that commonly used parameterizations significantly underestimate the effect of incomplete ionization in Al doped Si. Based on the experimental data, we propose new parameter values for the parameterization of incomplete ionization given in Altermatt et al., J. Appl. Phys. 100, 113715 (2006). Using these new values, the saturation current density J0,p+ of the Al-alloyed region of a standard silicon solar cell is determined by means of numerical device modeling. It is shown that the parameterization influences J0,p+ significantly. Additionally, the weakening effect of incomplete ionization on band gap narrowing (BGN) should be taken into account in modeling that aims to predict device behavior after changes made to the Al-alloyed region.

The Effect of Incomplete Ionization on the Turn-Off Behavior of FS IGBTs

This letter demonstrates for the first time the effect of the incomplete ionization (I.I.) of the transparent p-anode layer on the static and dynamic characteristics of the field-stop insulated gate bipolar transistors (FS IGBTs). This effect needs to be considered in FS IGBTs TCAD modeling to match accurately the device characteristics across a wide range of temperatures. The acceptor ionization energy (EA) governing the I.I. mechanism for the p-anode is extracted via matching the experimental turn-off waveforms and the static performance with Medici simulator.

Ultra-Responsive Phase Shifters for Depletion Mode Silicon Modulators

We propose a novel phase shifter design for carrier depletion based silicon modulators, based on an experimentally validated model. We note that the heretofore neglected effect of incomplete ionization will have a significant impact on ultra-responsive phase shifters. We predict a low VπL product of 0.31 V.cm associated with a low propagation loss of 20 dB/cm. This would enable significantly smaller Mach-Zehnder modulators to be constructed that nonetheless would have low drive voltages, with substantial decreases in insertion loss. The proposed fabrication process is of minimal complexity; in particular, no high-resolution lithographic step is required.

Effect of incomplete ionization for the description of highly aluminum-doped silicon

In this study we present an advanced method for precise modeling of highly aluminum-doped p+ silicon, leading to excellent agreement of numerical and experimental data within a broad range. We analyze the influence of different recombination mechanisms on the saturation current densities of Al-doped Si surfaces for different Al profiles. Lateral doping inhomogeneities and the effect of incomplete ionization have been examined in detail. We demonstrate that incomplete ionization affects the profile characteristics significantly and, therefore, has to be accounted for in accurate modeling of highly Al-doped silicon.

Accurate modeling of aluminum-doped silicon

Abstract We present a detailed study on accurate modeling of highly aluminum-doped p+ silicon. We have analyzed the influence of defect recombination and the effect of incomplete ionization on the saturation current densities of Al-p+ regions featuring different Al doping profiles. Very good agreement within a broad range of experimental data has been obtained. We demonstrate that incomplete ionization has a significant impact on the doping profile characteristics and, therefore, has to be accounted for in accurate modeling of highly aluminum-doped silicon.

Diffusion and activation of n-type dopants in germanium

The diffusion and activation of n-type impurities (P and As) implanted into p-type Ge(100) substrates were examined under various dose and annealing conditions. The secondary ion mass spectrometry profiles of chemical concentrations indicated the existence of a sufficiently high number of impurities with increasing implanted doses. However, spreading resistance probe profiles of electrical concentrations showed electrical concentration saturation in spite of increasing doses and indicated poor activation of As relative to P in Ge. The relationships between the chemical and electrical concentrations of P in Ge and Si were calculated, taking into account the effect of incomplete ionization. The results indicated that the activation of P was almost the same in Ge and Si. The activation ratios obtained experimentally were similar to the calculated values, implying insufficient degeneration of Ge. The profiles of P in Ge substrates with and without damage generated by Ge ion implantation were compared, and it was clarified that the damage that may compensate the activated n-type dopants has no relationship with the activation of P in Ge.

Device Modeling at Cryogenic Temperatures: Effects of Incomplete Ionization

We present a device performance modeling methodology that self-consistently resolves device operation at cryogenic temperatures (T > 30 K) in conjunction with incomplete ionization effects that take into account the change in dopant activation energies as a function of doping. Using this methodology, we developed a device simulator that predicts n-channel MOSFET (NMOSFET) device characteristics for a wide range of temperatures by solving semiconductor equations, along with the Poisson equation. Comparison of our calculated results with measurements shows that proper inclusion of variations in activation energy as a function of doping level is necessary for accurately monitoring device operation at cryogenic temperatures. Using dopant activation energies that are independent of doping levels leads to current rolloff and eventually device turn-off at low-temperature simulations. However, activation energy models that give lower activation energies for higher doping levels result in improved NMOSFET performance at colder temperatures, which agrees with experiments. Furthermore, calculations indicate that different incomplete ionization models affect the NMOSFET characteristics mainly through changes in the resistances of the heavily doped source and drain regions, and the substrate.

Acid‐susceptive material as a host phase of argon‐rich noble gas in the carbonaceous chondrite Ningqiang

Abstract— A fine‐grained dark inclusion in the Ningqiang carbonaceous chondrite consists of relatively pristine solar nebular materials and has high concentrations of heavy primordial rare gases. Trapped 36Ar concentration amounts to 6 times 10−6 cc STP/g, which is higher than that of Ningqiang host by a factor of three. Light HF‐HCl etching of the dark inclusion removed 86, 73, and 64% of the primordial 36Ar, 84Kr, and 132Xe, respectively. Thus, the majority of the noble gases in this inclusion are located in very acid‐susceptive material. Based on the elemental composition, the noble gases lost from the dark inclusion during the acid‐treatments are Ar‐rich, and the noble gases remaining in the inclusion are Q and HL gases. Transmission electron microscopy showed that the acid treatments removed thin Si, Mg, and Fe‐rich amorphous rims present around small olivine and pyroxene grains in the dark inclusion, suggesting that the Ar‐rich gases reside in the amorphous layers. A possible origin of the Ar‐rich gases is the acquisition of noble‐gas ions with a composition fractionated relative to solar abundance favoring the heavy elements by the effect of incomplete ionization under plasma conditions at 8000 K electron temperature.

Theoretical investigation of incomplete ionization of dopants in uniform and ion-implanted 4H-SiC MESFETs

The effects of incomplete ionization of nitrogen in 4H-SiC have been investigated. Poisson's equation is numerically analysed by considering the effects of Poole-Frenkel and the effects of the potential on N+d (the concentration of ionized donors) and n (the concentration of electrons). The pinch-off voltages of the uniform and the ion-implanted channels of 4H-SiC metal-semiconductor field-effect transistors (MESFETs) and the capacitance of the gate are given at different temperatures. Both the Poole-Frenkel effect and the potential have influence on the pinch-off voltage Vp of 4H-SiC MESFETs. Although the C-V characteristics of the ion-implanted and the uniform channel of 4H-SiC MESFETs have a clear distinction, the effects of incomplete ionization on the C-V characteristics are not significant.

Effects of incomplete ionization of impurities in poly-Si gate and band gap narrowing on direct tunneling gate leakage current

In this article the ionization rate of phosphorus doped in poly-Si gate and band gap narrowing caused by carrier–carrier interactions and carrier–ion interactions are self-consistently calculated by using a simple algorithm that is formulated phenomenologically. As a result, the ionization rate is found to be unity when the phosphorus concentration is less than 3×1019 cm−3, and becomes lower rapidly with the increase of the concentration larger than 3×1019 cm−3. Using this result, in a wide oxide voltage region, we can reproduce the oxide voltage dependence of the measured tunneling current from the gate in various samples (tOX=2.1, 2.8, and 3.4 nm) with the same tunneling mass (mOX=0.42m0), where m0 is the free electron mass. In particular, we show why the incomplete ionization can reproduce the tunneling current from the gate even in a lower oxide voltage region where the complete ionization cannot do so. Furthermore, a local band gap narrowing, which is described by an additional band gap narrowing due to exchange–correlation interactions of carriers induced by a local potential, is included in the present calculation.

Theoretical investigation of incomplete ionization of dopants in 6H–SiC metal-oxide-semiconductor capacitors

The effect of incomplete ionization of dopants on the capacitance–voltage (C–V) characteristics in 6H–SiC metal-oxide-semiconductor (MOS) capacitors has been investigated. The present exploration is based on the one-dimensional numerical solving of Poisson’s equation using the finite-difference method with a nonuniform mesh size. The results obtained from this approach are in good agreement with the first analytical results reported by Bouillon and Skotnicki in the case of indium impurities in silicon [IEEE Electron Device Lett. 19, 19 (1996)]. For p-type 6H–SiC material, characterized by deeper doping impurity energies (principally aluminum and boron), simulations predict the occurrence of a “kink effect” on the C–V curves, depending on temperature and doping level, that could lead to experimental errors in the extraction of MOS device parameters, including effective doping level, interface trap density, and fixed oxide charge.

N/sup +/-polysilicon gate PMOSFET's with indium doped buried-channels

A n/sup +/-polysilicon gate PMOSFET with indium doped buried-channel is discussed, The gate length scaling of n/sup +/-polysilicon gate buried-length PMOSFET's is limited by the channel punch-through effect. Designing shallow counter-doped layers (buried-channels) has been established as a means to reduce the undesirable short channel effects in these devices. Indium, an acceptor dopant in Si, has a low diffusion coefficient and implant statistics favorable for achieving shallow doping layers. Indium implants are explored (as an alternative to BF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) to counter dope the n-tub for adjusting the threshold voltage. Devices are fabricated using AT&T's 0.5 μm CMOS technology but with t/sub ox/=50 /spl Aring/. Although no special effort has been made to optimize the n-tub or to take full advantage of the diffusion and implant characteristics of indium, excellent electrical results are obtained for devices with L/sub eff/=0.25 μm. Improved V/sub th/ roll-off characteristics and reduced body effect (/spl gamma//spl ap/0.18 V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> 2 / versus /spl gamma//sub B//spl ap/0.40 V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> 2 /) in indium implanted buried channels are demonstrated over BF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> implanted buried channels for PMOSFET's with identical long channel threshold voltages. The effects of incomplete ionization (freeze-out) of the indium acceptor states on the electrical device characteristics are demonstrated by device simulations and measurements.

Effects of incomplete ionization of impurity dopants on the performance of bipolar junction transistors

Effects of incomplete ionization of impurity dopants on the performance of bipolar junction transistors

Early stages of light interaction with solids at extreme intensities

Electron and radiation transport of energy is treated by self-similar methods in aluminium targets exposed to extreme radiation intensities. Detailed numerical solution of this phenomenon are given including the effects of incomplete ionization on the conduction processes and the internal energy.