Local Lifetime Research Articles

Exploration of Power Device Reliability Using Compact Device Models and Fast Electrothermal Simulation

This paper presents the application of compact insulated gate bipolar transistor and p-i-n diode models, including features such as local lifetime control and field-stop technology, to the full electrothermal system simulation of a hybrid electric vehicle converter using a lookup table of device losses. The vehicle converter is simulated with an urban driving cycle (the federal urban driving schedule), which is used to generate transient device temperature profiles. A methodology is also described to explore the converter reliability using the temperature profile, with rainflow cycle counting techniques from material fatigue analysis. The effects of ambient temperature, driving style, and converter design on converter reliability are also investigated.

Physical Modeling of Fast p-i-n Diodes With Carrier Lifetime Zoning, Part I: Device Model

This paper presents the development and implementation of a physics-based diode model which can simulate aspects of high-voltage diodes such as snappy recovery during punch-through and the modified carrier density profile due to local lifetime control. It uses a Fourier series solution for the ambipolar diffusion equation in the lightly doped base region. The model is compared with finite-element device simulations. A parameter extraction procedure for the diode with lifetime control is proposed in Part II.

Dynamic avalanche in diodes with local lifetime control by means of palladium

The increase of the static breakdown voltage and the reduction of dynamic avalanche in a fast recovery 2.5kV/150A P-i-N diode subjected to the radiation enhanced diffusion of a palladium are discussed. The in-diffusing palladium compensates the doping profile in a lightly doped N-base close to the anode junction. Using a device simulation, the increase of the breakdown voltage and the reduction of the dynamic avalanche are explained by the reduction of peak electric field in the additional low-doped P-type layer created by the compensation effect. This is presented for both a dc and transient device operation and confirmed experimentally as well. An improved technology curve for the static versus recovery losses at a high line voltage has been obtained. A high thermal budget of deep levels and a low leakage current are additional benefits of the method.

Electrically probing photonic bandgap phenomena in contacted defect nanocavities

We demonstrate an electrically tunable two dimensional photonic crystal nanocavity containing InAs self-assembled quantum dots (QDs). Photoluminescence and electroluminescence measurements are combined to probe the cavity mode structure and demonstrate a local electrical contact to the quantum dots. Measurements performed as a function of the electric field enable us to probe the capture, relaxation, and recombination dynamics of photogenerated carriers inside the quantum dots emitting into a modified photonic environment. Furthermore, the two dimensional photonic crystal is probed by spatially dependent photocurrent spectroscopy indicating a 3.5× enhancement of the local radiative lifetime of the QDs inside the photonic crystal environment.

An Analytical Model of an OCVD-Based Measurement Technique of the Local Carrier Lifetime

A model of a new technique to measure the spatial distribution of the majority and minority carrier lifetime along epilayers is presented. Being in good agreement with simulations, this model clarifies the behavior of the test structure used in the technique and gives a physical interpretation of the measured quantities.

Radiation-Enhanced Diffusion of Palladium for a Local Lifetime Control in Power Devices

Palladium (Pd) diffusion from a surface layer enhanced by defects from a helium (He) irradiation is shown to provide a local lifetime control in a power p-i-n diode annealed between 350degC and 700degC. An open-circuit voltage decay lifetime measurement is used to identify temperature ranges in which one of two lifetime control mechanisms takes part. Spreading resistance measurements show the doping compensation at the anode junction caused by defects after the Pd diffusion below 725degC. Locally modified doping profiles by introduced defects cause significantly lowered dynamic avalanche (DA) during fast reverse recovery compared to the standard He irradiation as confirmed also by device simulation. Advanced shaping of a shallow doping profile, reducing avalanche generation in the area of peaking electric field under a reverse bias, is suggested as an additional method to suppress the DA in power devices. The diffusion at 650degC gives the best static and dynamic parameters. Breakdown voltage and leakage current are those of untreated diode. Turn-off losses close to the SOA limit are also much lower than in the standard He irradiation, and thermal characteristics are better than after the traditional high-temperature diffusion.

Improvement of 4H-SiC Power p-i-n Diode Switching Performance Through Local Lifetime Control Using Boron Diffusion

A comparison is carried out of the switching characteristics of 4H-SiC conventional p-i-n rectifiers, where the p-layer is formed by aluminum doping during epitaxial growth, with that of p-i-n diodes, where the p-layer is formed by codiffusion of aluminum and boron. It is demonstrated that p-i-n diodes that are produced by high-temperature diffusion exhibit better switching capability as compared to epigrown p-i-n diodes. The improved behavior is attributed to the reduced lifetime region that is created by the diffused boron layer. Also, the reduced lifetime region was implemented in a SiC conventional epitaxial p-i-n structure by boron diffusion through the epitaxial aluminum-doped p+ layer; the switching behavior of such a hybrid p-i-n diode is identical to that of the diffused one. The improvement of reverse-recovery characteristic is attributed to the effect of localized lifetime control by recombination centers that are created by diffused boron

Spatial variations of doping and lifetime in epitaxial laterally overgrown GaN

Spatial variations of donor concentration and diffusion length/lifetime were studied for epitaxial laterally overgrown undoped n-GaN samples by electron beam induced current (EBIC) and microcathodoluminescence (MCL). The dependence of the EBIC signal collection efficiency on the probing beam accelerating voltage shows that the local electron concentration is three times lower and the local lifetime about twice as high in the laterally overgrown regions compared to the regions grown in the SiO2 mask windows. Band edge MCL profiling shows that the lifetime difference could be an order of magnitude higher. EBIC scans along the SiO2 stripes in the low dislocation density overgrown regions show long propagation distances of holes in the quasineutral part of the structure, explained by the existence of a potential profile forming a trough for transport of holes while spatially separating nonequilibrium carriers.

Effect of Proton Irradiation Dose on the Gettering Efficiency of Platinum and the Performance of Local Lifetime-Controlled Power Diodes

On the basis of the proximity gettering of platinum by vacancy defects which are induced by proton irradiation, local platinum doping is realized. This method is used as a local lifetime control technology for high-power diodes. The theoretical dependence of electrically active Pt concentration CPtS on the concentration of irradiation-induced defects CV, is also studied. The diodes' reverse performance parameters are measured. At low proton irradiation doses, the quantities of platinum gettered by irradiation-induced defects are enhanced when the irradiation dose increases. This can improve the device's performance. When the proton irradiation dose is high enough, the peak concentration of gettered platinum tends to saturate. This is consistent with the theoretical result.

Local lifetime control in silicon power diode by ion irradiation: introduction and stability of shallow donors

Enhanced formation of shallow donors (SDs) in hydrogen or helium-irradiated and subsequently annealed float‐zone n-type silicon is investigated. Ion energies, irradiation fluences and annealing temperatures were chosen in ranges typically used for local lifetime control in silicon power devices. Introduced radiation defects and SDs were investigated by deep-level transient spectroscopy and C–V profiling. Results show that radiation damage produced by helium ions remarkably enhances formation of thermal donors (TDs) when the annealing temperature exceeds 375°C, i.e. when the majority of vacancy-related recombination centres anneal out. Proton irradiation introduces hydrogen donors (HDs) which form a Gaussian peak at the proton end-of-range. Their concentration linearly increases with proton fluence and changes dramatically during post-irradiation annealing between 100 and 200°C since HD constituents are reacting with radiation damage. Their annealing in this temperature range is influenced by the electric field. If annealing temperature exceeds 400°C, HDs disappear and the excessive shallow doping is caused, as in the case of helium irradiation, by TDs enhanced by radiation damage. Shallow doping introduced by both hydrogen and helium can have a detrimental influence on blocking voltage of power diodes if high irradiation fluences or wrong annealing conditions are chosen.

Online Multicasting for Network Capacity Maximization in Energy-Constrained Ad Hoc Networks

In this paper, we present new algorithms for online multicast routing in ad hoc networks where nodes are energy-constrained. The objective is to maximize the total amount of multicast message data routed successfully over the network without any knowledge of future multicast request arrivals and generation rates. Specifically, we first propose an online algorithm for the problem based on an exponential function of energy utilization at each node. The competitive ratio of the proposed algorithm is analyzed if admission control of multicast requests is permitted. We then provide another online algorithm for the problem, which is based on minimizing transmission energy consumption for each multicast request and guaranteeing that the local network lifetime is no less than \gamma times of the optimum, where \gamma is constant with 0 < \gamma\leq 1. We finally conduct extensive experiments by simulations to analyze the performance of the proposed algorithms, in terms of network capacity, network lifetime, and transmission energy consumption for each multicast request. The experimental results clearly indicate that, for online multicast routing in ad hoc wireless networks, the network capacity is proportional to the network lifetime if the transmission energy consumption for each multicast request is at the same time minimized. This is in contrast to the implication by Kar et al. that the network lifetime is proportional to the network capacity when they considered the online unicast routing by devising an algorithm based on the exponential function of energy utilization at each node.

양성자가 주입된 NPT형 전력용 다이오드의 전류-전압 특성

Local minority carrier lifetime control by means of particle irradiation is an useful technology for Production of modern silicon Power devices. Crystal damage due to ion irradiation can be easily localized by choosing appropriate irradiation energy and minority tarrier lifetime can be reduced locally only in the damaged layer. In this work, proton irradiation technology was used for improving the switching characteristics of a un diode. The irradiation was carried out with various energy and dose condition. The device was characterized by current-voltage, capacitance-voltage, and reverse recovery time measurements. Forward voltage drop was increased to 1.1 V at forward current of 5 A, which was of its original device. Reverse leakage current was 64 nA at reverse voltage of 100 V, and reverse breakdown voltage was 670 V which was the same voltage as original device without irradiation. The reverse recovery time of device was reduced to about compared to that of original device without irradiation.

A WKB solution of excess carriers in conductivity modulation base with non-uniform lifetime

Base on the establishment of an ambipolar transport equation of conductivity modulation base with non-uniform lifetime, WKB solutions of excess carrier profiles under different boundary conditions have been obtained by using Liouville-Green transform. The results can be used in modeling of conductivity modulation power devices under localized lifetime control.

On-line disjoint path routing for network capacity maximization in energy-constrained ad hoc networks

In this paper we consider on-line disjoint path routing in energy-constrained ad hoc networks. The objective is to maximize the network capacity, i.e. maximize the number of messages routed successfully by the network without any knowledge of future disjoint path connection request arrivals and generation rates. Specifically, in this paper we first present two centralized on-line algorithms for the problem. One is based on maximizing local network lifetime, which aims to minimize the transmission energy consumption, under the constraint that the local network lifetime is no less than γ times of the optimum after the realization of each disjoint path connection request, where γ is constant with 0 < γ ⩽ 1. Another is based on the exponential function of energy utilization at nodes, and the competitive ratio of this latter algorithm is also analyzed if admission control mechanism is employed. We then conduct extensive experiments by simulations to analyze the performance of the proposed algorithms, in terms of network capacity, network lifetime, and the transmission energy consumption for each disjoint path connection request. The experimental results show that the proposed algorithms outperform those existing algorithms that do not take into account the power load balancing at nodes in terms of maximizing the network capacity.

High-power P-i-N diode with local lifetime control using palladium diffusion controlled by radiation defects

We demonstrate for the first time a high-power P-i-N diode with local lifetime control using palladium (Pd) diffusion. Low-temperature (600/spl deg/C-700/spl deg/C) diffusion of Pd is stimulated by radiation defects resulting from alpha-particle irradiation ( <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> He/sup 2+/: 10 MeV, 10/sup 12/ cm/sup -2/). The region of maximal radiation damage of Gaussian shape is decorated by substitutional Pd after diffusion from a palladium silicide surface layer through the P/sup +/--P region into the N-base close to the anode junction. Significantly lower leakage current compared to that of standard <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> He/sup 2+/ irradiation and very good ruggedness under fast recovery (di/dt/spl ap/500 A/μs, V/sub R//spl ap/2 kV) is demonstrated for Pd diffusion at 600/spl deg/C.

Lifetime control in silicon power P-i-N diode by ion irradiation: Suppression of undesired leakage

The irradiation with high-energy (7.35MeV) protons through a set of energy degraders was used to suppress leakage of the silicon power diodes subjected to local lifetime control. The aim was to modify the profile of recombination centers and to reduce production of vacancy complexes. The high-energy proton irradiation was compared with standard local lifetime killing by high-energy alphas. Recombination centers arising from irradiation were characterized after irradiation and subsequent annealing at 220 and 350°C by deep level transient spectroscopy and I–V profiling. Static and dynamic parameters of irradiated diodes were also measured and compared. Results show that the applied irradiation with protons provides 3–10 times lower leakage compared to standard alphas for equivalent reduction of the reverse recovery current maximum. On the other hand, the excessive formation of hydrogen donors at high proton fluences and their diffusion during annealing at 350° decreases diode blocking capability.

Hydrogen and helium interactions in Si: phenomena obscure and not-so-obscure

The deliberate use of H- and He-related phenomena in crystalline Si (c-Si) has at times been hampered by concerns of the mobility of these light elements and hence potential device instability. However H is inevitably present in many Si processing steps, though not necessarily in the finished device. Accordingly one could differentiate between a transient or catalytic interaction of H with c-Si, and one where H resides permanently during device operation. We have uncovered phenomena on both domains, and these involve trapping and de-trapping of H by defective regions, thermal activation of latent defects in hydrogenated c-Si, and low-temperature activation of ion implanted dopant atoms. He differs from H principally by its electrical inactivity, but plays a significant role in altering the microstructure. The strong interaction of He with vacancy clusters results in nanocavities that act as excellent gettering sites and also enable localized minority carrier lifetime control. H and He thus offer possibilities for defect and impurity engineering in Si.

Correction to "Characterization of Recombination Centers in Si Epilayers After Helium Implantation by Direct Measurement of Local Lifetime Distribution with the AC Lifetime Profiling Technique"

Correction to "Characterization of Recombination Centers in Si Epilayers After Helium Implantation by Direct Measurement of Local Lifetime Distribution with the AC Lifetime Profiling Technique"

양성자 조사법에 의한 고속스위칭 사이리스터의 제조

A fast switching thyristor with a superior trade-off property between the on-state voltage drop and the turn-off time could be fabricated by the proton irradiation method. After making symmetric thyristor dies with a voltage rating of 1,600 V from 350 <TEX>$\mu$</TEX>m thickness of 60 <TEX>$\Omega$</TEX>ㆍcm NTD-Si wafer and 200 <TEX>$\mu$</TEX>m width of n-base drift layer, the local carrier lifetime control by the proton irradiation was performed with help of the HI-13 tandem accelerator in China. The thyristor samples irradiated with 4.7 MeV proton beam showed a superior trade-off relationship of <TEX>$V_{TM}$</TEX> = 1.55 V and <TEX>$t_{q}$</TEX> = 15 <TEX>$\mu$</TEX>s attributed to a very narrow layer of short carrier lifetime(～1 <TEX>$\mu$</TEX>s) in the middle of its n-base drift region. To explain the small increase of <TEX>$V_{TM}$</TEX> , we will introduce the effect of carrier compensation at the low carrier lifetime region by the diffusion current.ffusion current.t.

Characterization of Recombination Centers in Si Epilayers After He Implantation by Direct Measurement of Local Lifetime Distribution With the AC Lifetime Profiling Technique

The distribution of recombination centers induced in Si epi-substrates by helium (He) implantation is obtained for the first time by direct measurement of local recombination lifetime profile along the layer, using the ac differential lifetime profiling technique. The different energy levels of the recombination centers induced by He implantation at different doses and energies have been extracted, as a function of the position in the layer, by temperature scanning of the lifetime profiles. The lifetime measurements clearly demonstrate the presence of a secondary defect distribution that extend from the region of maximum primary damage both at lower and higher depths respect to the stopping range depth, due to the relatively large concentration of primary defects created near the stopping range, and give a coherent picture of the effects of He implant on the "local" lifetime.