SwePub - sökning: WFRF:(Domeij Martin)

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1.	Badel, Xavier, et al. (författare) Doping of electrochemically etched pore arrays in n-type silicon : processing and electrical characterization 2005 Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 152:4, s. G252-G258 Tidskriftsartikel (refereegranskat)abstract Silicon p-n diodes formed in the walls of deep pores have been electrically characterized. The pores were electrochemically etched in low-doped n-type silicon substrates, and the entire pore array was doped p(+) by boron diffusion at 1050 degrees C. Two different process flows were investigated to disconnect the p(+) layers from one pore to another. The first consists of removing a few micrometers of silicon at the top of the sample using reactive ion etching after diffusion while the second enables the prevention of doping at the top of the pore walls with an oxide, acting as a barrier during diffusion. Current-voltage and capacitance-voltage characteristics of p-n junctions are presented and related parameters, such as the serial resistance and the ideality factor are discussed. The results show good rectifying behavior of the diodes with a reverse current about four to five decades smaller than the forward current. Measurements with two pores connected in a transistor-like configuration (p(+)/n(-)/p(+)), were also performed. Device simulations were used to examine the device behavior. Finally, our results demonstrate that pores could work as individual detector pixels for moderate reverse voltages, suitable for radiation imaging applications.
2.	Buchholt, Kristina, et al. (författare) Growth and characterization of epitaxial Ti3GeC2 thin films on 4H-SiC(0001) 2012 Ingår i: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 343:1, s. 133-137 Tidskriftsartikel (refereegranskat)abstract Epitaxial Ti3GeC2 thin films were deposited on 4 degrees off-cut 4H-SiC(0001) using magnetron sputtering from high purity Ti, C, and Ge targets. Scanning electron microscopy and helium ion microscopy show that the Ti3GeC2 films grow by lateral step-flow with {11 (2) over bar0} faceting on the SiC surface. Using elastic recoil detection analysis, atomic force microscopy, and X-Ray diffraction the films were found to be substoichiometric in Ge with the presence of small Ge particles at the surface of the film.
3.	Buchholt, Kristina, et al. (författare) Ohmic contact properties of magnetron sputtered Ti3SiC2 on n- and p-type 4H-silicon carbide 2011 Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 98:4, s. 042108- Tidskriftsartikel (refereegranskat)abstract Epitaxial Ti3SiC2 (0001) thin film contacts were grown on doped 4H-SiC (0001) using magnetron sputtering in an ultra high vacuum system. The specific contact resistance was investigated using linear transmission line measurements. Rapid thermal annealing at 950 degrees C for 1 min of as-deposited films yielded ohmic contacts to n-type SiC with contact resistances in the order of 10(-4) Omega cm(2). Transmission electron microscopy shows that the interface between Ti3SiC2 and n-type SiC is atomically sharp with evidence of interfacial ordering after annealing. (c) 2011 American Institute of Physics.
4.	Buono, Benedetto, et al. (författare) Current Gain Degradation in 4H-SiC Power BJTs 2011 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 679-680, s. 702-705 Tidskriftsartikel (refereegranskat)abstract SiC airs are very attractive for high power application, but long term stability is still problematic and it could prohibit commercial production of these devices. The aim of this paper is to investigate the current gain degradation in BJTs with no significant degradation of the on-resistance. Electrical measurements and simulations have been used to characterize the behavior of the BJT during the stress test. Current gain degradation occurs, the gain drops from 58 before stress to 43 after 40 hours, and, moreover, the knee current shows fluctuations in its value during the first 20 hours. Current gain degradation has been attributed to increased interface traps or reduced lifetime in the base-emitter region or small stacking faults in the base-emitter region, while fluctuations of the knee current might be due to stacking faults in the collector region.
5.	Buono, Benedetto, et al. (författare) Influence of Emitter Width and Emitter-Base Distance on the Current Gain in 4H-SiC Power BJTs 2010 Ingår i: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 57:10, s. 2664-2670 Tidskriftsartikel (refereegranskat)abstract The influence of the emitter-base geometry on the current gain has been investigated by means of measurements and simulations. Particular attention has been placed on the emitter width and on the distance between the emitter edge and the base contact. When the emitter width is decreased from 40 to 8 mu m, the current gain is reduced by 20%, whereas when the distance between the base contact and the emitter edge is decreased from 5 to 2 mu m, the current gain is reduced by 10%. Simulations have been used to investigate the reasons for the current gain reduction. The reduction of the emitter width induces two mechanisms of current gain reduction: earlier forward biasing of the base-collector junction and higher recombination in the emitter region. Both mechanisms result from the higher current density flowing under the emitter region. Placing the base contact very close to the emitter edge increases the base current by increasing the gradient of the electron concentration toward the base contact. The effect of increasing the base doping in the extrinsic region has been simulated, and the results demonstrate that the current gain can be improved if a high doping concentration in the range of 5 x 10(18) cm(-3) is used.
6.	Buono, Benedetto, et al. (författare) Investigation of Current Gain Degradation in 4H-SiC Power BJTs 2012 Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 717-720, s. 1131-1134 Tidskriftsartikel (refereegranskat)abstract The current gain degradation of 4H-SiC BJTs with no significant drift of the on-resistance is investigated. Electrical stress on devices with different emitter widths suggests that the device design can influence the degradation behavior. Analysis of the base current extrapolated from the Gummel plot indicates that the reduction of the carrier lifetime in the base region could be the cause for the degradation of the gain. However, analysis of the base current of the base-emitter diode shows that the degradation of the passivation layer could also influence the reduction of the current gain.
7.	Buono, Benedetto, et al. (författare) Modeling and Characterization of Current Gain Versus Temperature in 4H-SiC Power BJTs 2010 Ingår i: IEEE Transactions on Electron Devices. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9383 .- 1557-9646. ; 57:3, s. 704-711 Tidskriftsartikel (refereegranskat)abstract Accurate physical modeling has been developed to describe the current gain of silicon carbide (SiC) power bipolar junction transistors (BJTs), and the results have been compared with measurements. Interface traps between SiC and SiO2 have been used to model the surface recombination by changing the trap profile, capture cross section, and concentration. The best agreement with measurement is obtained using one single energy level at 1 eV above the valence band, a capture cross section of 1 x 10(-15) cm(2), and a trap concentration of 2 x 10(12) cm(-2). Simulations have been performed at different temperatures to validate the model and characterize the temperature behavior of SiC BJTs. An analysis of the carrier concentration at different collector currents has been performed in order to describe the mechanisms of the current gain fall-off at a high collector current both at room temperature and high temperatures. At room temperature, high injection in the base ( which has a doping concentration of 3 x 10(17) cm(-3)) and forward biasing of the base-collector junction occur simultaneously, causing an abrupt drop of the current gain. At higher temperatures, high injection in the base is alleviated by the higher ionization degree of the aluminum dopants, and then forward biasing of the base-collector junction is the acting mechanism for the current gain fall-off. Forward biasing of the base-collector junction can also explain the reduction of the knee current with increasing temperature by means of the negative temperature dependence of the mobility.
8.	Buono, Benedetto, et al. (författare) Modeling and Characterization of the ON-Resistance in 4H-SiC Power BJTs 2011 Ingår i: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 58:7, s. 2081-2087 Tidskriftsartikel (refereegranskat)abstract The ON-resistance of silicon carbide bipolar transistors is characterized and simulated. Output characteristics are compared at different base currents and different temperatures in order to validate the physical model parameters. A good agreement is obtained, and the key factors, which limit the improvement of R-ON, are identified. Surface recombination and material quality play an important role in improving device performances, but the device design is also crucial. Based on simulation results, a design that can enhance the conductivity modulation in the lowly doped drift region is proposed. By increasing the base doping in the extrinsic region, it is possible to meet the requirements of having low voltage drop, high current density, and satisfactory forced current gain. According to simulation results, if the doping is 5 x 10(18) cm(-3), it is possible to conduct 200 A/cm(2) at V-CE = 1 V by having a forced current gain of about 8, which represents a large improvement, compared with the simulated value of only one in the standard design.
9.	Buono, Benedetto (författare) Simulation and Characterization of Silicon Carbide Power Bipolar Junction Transistors 2012 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The superior characteristics of silicon carbide, compared with silicon, have suggested considering this material for the next generation of power semiconductor devices. Among the different power switches, the bipolar junction transistor (BJT) can provide a very low forward voltage drop, a high current capability and a fast switching speed. However, in order to compete on the market, it is crucial to a have high current gain and a breakdown voltage close to ideal. Moreover, the absence of conductivity modulation and long-term stability has to be solved. In this thesis, these topics are investigated comparing simulations and measurements. Initially, an efficient etched JTE has been simulated and fabricated. In agreement with the simulations, the fabricated diodes exhibit the highest BV of around 4.3 kV when a two-zone JTE is implemented. Furthermore, the simulations and measurements demonstrate a good agreement between the electric field distribution inside the device and the optical luminescence measured at breakdown. Additionally, an accurate model to simulate the forward characteristics of 4H-SiC BJTs is presented. In order to validate the model, the simulated current gains are compared with measurements at different temperatures and different base-emitter geometries. Moreover, the simulations and measurements of the on-resistance are compared at different base currents and different temperatures. This comparison, coupled with a detailed analysis of the carrier concentration inside the BJT, indicates that internal forward biasing of the base-collector junction limits the BJT to operate at high current density and low forward voltage drop simultaneously. In agreement with the measurements, a design with a highly-doped extrinsic base is proposed to alleviate this problem. In addition to the static characteristics, the comparison of measured and simulated switching waveforms demonstrates that the SiC BJT can provide fast switching speed when it acts as a unipolar device. This is crucial to have low power losses during transient. Finally, the long-term stability is investigated. It is observed that the electrical stress of the base-emitter diode produces current gain degradation; however, the degradation mechanisms are still unclear. In fact, the analysis of the measured Gummel plot suggests that the reduction of the carrier lifetime in the base-emitter region might be only one of the causes of this degradation. In addition, the current gain degradation due to ionizing radiation is investigated comparing the simulations and measurements. The simulations suggest that the creation of positive charge in the passivation layer can increase the base current; this increase is also observed in the electrical measurements.
10.	Buono, Benedetto, et al. (författare) Simulations of Open Emitter Breakdown Voltage in SiC BJTs with non Implanted JTE 2009 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 615-617, s. 841-844 Tidskriftsartikel (refereegranskat)abstract Ion implantation for selective doping of SiC is problematic due to damage generation during the process and low activation of dopants. In SiC bipolar junction transistor (BJT) the junction termination extension (JTE) can be formed without ion implantation using instead a controlled etching into the epitaxial base. This etched JTE is advantageous because it eliminates ion implantation induced damage and the need for high temperature annealing. However, the dose, which is controlled by the etched base thickness and doping concentration, plays a crucial role. In order to find the optimum parameters, device simulations of different etched base thicknesses have been performed using the software Sentaurus Device. A surface passivation layer consisting of silicon dioxide, considering interface traps and fixed trapped charge, has been included in the analysis by simulations. Moreover a comparison with measured data for fabricated SiC BJTs has been performed.
11.	Buono, Benedetto, et al. (författare) Temperature Modeling and Characterization of the Current Gain in 4H-SiC Power BJTs 2010 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 645-648, s. 1061-1064 Tidskriftsartikel (refereegranskat)abstract The current gain of 4H-SiC BJTs has been modeled using interface traps between SIC and SiO2 to describe surface recombination, by a positive temperature dependence of the carrier lifetime in the base region and by bandgap narrowing in the emitter region. The interface traps have been modeled by one single level at 1 eV above the valence band, with capture cross section of 1 x 10(-15) cm(2) and concentration of 2 x 10(12) cm(-2). The temperature behavior of SiC BJTs has been simulated and the results have been compared with measurements. An analysis of the carrier concentration has been performed in order to describe the mechanisms for fall-off of the current gain at high collector current. At room temperature high injection in the base and forward biasing of the base-collector junction occur simultaneously causing an abrupt drop of the current gain. At higher temperatures high injection in the base is alleviated by the higher ionization degree of the aluminum dopants, and then forward biasing of the base-collector junction is the only acting mechanism for the current gain fall-off at high collector current. This mechanism and the negative temperature dependence of the carrier mobility can also explain the reduction of the knee current for gain fall-off with increasing temperature. Simulations with different emitter widths have been also performed and analyzed to characterize the emitter size effect. Higher current density caused by reducing the emitter width introduces higher carrier recombination in the emitter region, leading to a reduction of the current gain.
12.	Chen, M., et al. (författare) A novel diode structure with controlled injection of backside holes (CIBH) 2006 Konferensbidrag (refereegranskat)abstract In this paper we present a novel 3.3kV diode structure with controlled injection of backside holes, i.e. CIBH diode. This new diode structure features buried floating p layers at the cathode side. These p doped areas prevent the formation of high electric field strength at the nn+ junction and accordingly avoid the avalanche generation at the nn+ junction. The CIBH diode concept provides, compared to diodes without p layers and the same design, significantly improved dynamic ruggedness and improved sott reverse recovery at low current densities. Simulations and results of the first fabricated diodes show the readability of this new promising diode concept.
13.	Danielson, E., et al. (författare) Investigation of thermal properties in fabricated 4H-SiC high power bipolar transistors 2003 Ingår i: Solid-State Electronics. - 0038-1101 .- 1879-2405. ; 47:4, s. 639-644 Tidskriftsartikel (refereegranskat)abstract Silicon carbide bipolar junction transistors have been fabricated and investigated. The transistors had a maximum current gain of approximately 10 times, and a breakdown voltage of 450 V. When operated at high power densities the device showed a clear self-heating effect, decreasing the current gain. The junction temperature was extracted during self-heating to approximately 150 degreesC, using the assumption that the current gain only depends on temperature. Thermal images of a device under operation were also recorded using an infrared camera, showing a significant temperature increase in the vicinity of the device. The device was also tested in a switched setup, showing fast turn on and turn off at 1 MHz and 300 V supply voltage. Device simulations have been used to analyze the measured data. The thermal conductivity is fitted against the self-heating, and the lifetime in the base is fitted against the measurement of the current gain.
14.	Danielsson, Erik, et al. (författare) A 4H-SiC BJT with an epitaxially regrown extrinsic base layer 2005 Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 483, s. 905-908 Tidskriftsartikel (refereegranskat)abstract 4H-SiC BJTs were fabricated using epitaxial regrowth instead of ion implantation to form a highly doped extrinsic base layer necessary for a good base ohmic contact. A remaining p(+) regrowth spacer at the edge of the base-emitter junction is proposed to explain a low current gain of 6 for the BJTs. A breakdown voltage of 1000 V was obtained for devices with Al implanted JTE.
15.	Danielsson, Erik, et al. (författare) Extrinsic base design of SiC bipolar transistors 2004 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 457-460:II, s. 1117-1120 Tidskriftsartikel (refereegranskat)abstract The SiC npn bipolar junction transistor (BJT) is a very promising device for high voltage and high power switches. The SiC BJT has, due to junction voltage cancellation, potentially a low on-resistance. However, the high resistivity in the base layer can induce a locally forward biased base collector junction and a premature current from the base to collector at on-state. In this work we propose a new technique to fabricate the extrinsic base using regrowth of the extrinsic base layer. This technique can put the highly doped region of the extrinsic base a few tenths of a micron from the intrinsic region. We also propose a new mobility model in our simulations to correctly account for the ionized impurities in minority carrier transport and elevated temperature.
16.	Domeij, David, et al. (författare) Inequality Trends in Sweden 1978-2004 2010 Ingår i: Review of economic dynamics. - : Elsevier BV. - 1094-2025 .- 1096-6099. ; 13:1, s. 179-208 Tidskriftsartikel (refereegranskat)abstract We document a clear increase in Swedish earnings inequality in the early 1990s, andthat much of this increase was generated by movements in and out of the labor market.Inequality in disposable income and earnings net of taxes and transfers also increased,but much less than the increased inequality in pre-government earnings. These di¤er-ent developments are most likely explained by the generous Swedish welfare system.Consistent with these observations, we see no clear trend in consumption inequality.We also estimate stochastic processes for household earnings. A simple random-walkprocess captures much of the life-cycle dynamics. But we .nd clear evidence that thetrue earnings process is not a random walk. We demonstrate that some estimationmethods result in severe upward bias in the estimated volatility of permanent shocksif serial correlation in temporary shocks is ignored.Our estimation results show that the increase in earnings inequality is almost entirelydriven by an increase in residualearnings inequality. Moreover, this increase wasmostly generated by an increased volatility of persistent shocks.
17.	Domeij, David, et al. (författare) Population Aging and International Capital Flows 2003 Annan publikation (övrigt vetenskapligt/konstnärligt)abstract We use the neoclassical growth framework to model international capital flows in a world with exogenous demographic change. We compare model implications and actual current account data and find that the model explains a small but significant fraction of capital flows between OECD countries, in particular after 1985. JEL classification: E22; F21; F41; F47
18.	Domeij, David, et al. (författare) The labor-supply elasticity and borrowing constraints : Why estimates are biased 2001 Annan publikation (övrigt vetenskapligt/konstnärligt)abstract The labor-supply elasticity is a central element in many macroeconomic models. We argue that assumptions underlying previous econometric estimates of the intertemporal labor supply elasticity are inconsistent with incomplete markets economies. In particular, if the econometrician ignores borrowing constraints, the elasticity will be biased downwards. Within our model, the bias may be up to 50 percent. We find a similar bias in PSID data.
19.	Domeij, Martin, et al. (författare) 2.2 kV SiC BJTs with low V(CESAT) fast switching and short-circuit capability 2010 Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2009, PTS 1 AND 2. ; , s. 1033-1036 Konferensbidrag (refereegranskat)abstract This paper reports large active area (15 mm(2)) 4H-SiC BJTS with a low V(CESAT)=0.6 V at 1(C)=20 A (J(C)=133 A/cm(2)) and an open-base breakdown voltage BV(CEO)=2.3 kV at T=25 degrees C. The corresponding room temperature specific on-resistance R(SP.ON)=4.5 m Omega cm(2) is to the authors knowledge the lowest reported value for a large area SiC BJT blocking more than 2 kV. The onstate and blocking characteristics were analyzed by device simulation and found to be in good agreement with measurements. Fast switching with VcE rise- and fall-times in the range of 20-30 ns was demonstrated for a 6 A 1200 V rated SiC BJT. It was concluded that high dynamic base currents are essential for fast switching to charge the BJT parasitic base-collector capacitance. In addition, 10 mu s short-circuit capability with V(CE)=800 V was shown for the 1200 V BJT.
20.	Domeij, Martin, et al. (författare) Analysis of the base current and saturation voltage in 4H-SiC power BJTs 2007 Ingår i: 2007 European Conference On Power Electronics And Applications. - 9789075815115 ; , s. 2744-2750 Konferensbidrag (refereegranskat)abstract Silicon carbide (SiC) power bipolar junction transistors are interesting competitors to Si IGBTs for 1200 V power electronics applications. Advantages of SiC BJTs are low collector-emitter saturation voltages, little stored charge and high temperature capability. In this work, SiC NPN power BJTs with common emitter current gains of 40 have been fabricated and characterized. Electrical measurements for BJTs with different emitter widths indicate that the current gain is limited by surface recombination. A low value of V-CESAT=0.9 V at J(C)=100 A/cm(2) was obtained for small and large area (3.4 mm(2)) BJTs and correlated with the formation of low-resistive ohmic contacts to the base. Large area BJTs were shown to operate with a current gain of 48 in pulsed mode at a collector current of 12 A corresponding to J(C)=360 A/cm(2).
21.	Domeij, Martin, et al. (författare) Avalanche Injection in High Voltage Si P-i-N Diodes Measurements and Device Simulations 1997 Ingår i: ISPSD '97. - 0780339940 - 0780339932 - 0780339959 ; , s. 125- Konferensbidrag (övrigt vetenskapligt/konstnärligt)
22.	Domeij, Martin, et al. (författare) Avalanche injection in high voltage Si PiN diodes 1997 Ingår i: Physica scripta. T. - 0281-1847. ; T69, s. 134-137 Tidskriftsartikel (refereegranskat)abstract An experimental technique using optical excitation by a YAG laser pulse for studying avalanche injection in power devices is demonstrated This technique enables the creation of high uniform excess carrier concentrations in an optically defined device volume, involving very little heating. A method for determining the onset of avalanche multiplication, by studying the time integral of the reverse recovery current, is proposed. A PiN diode is observed to turn off from avalanching at a dissipated power density of more than 200 kW/cm(2).
23.	Domeij, Martin, et al. (författare) Current gain dependence on emitter width in 4H-SiC BJTs 2006 Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 9780878494255 ; 527-529, s. 1425-1428 Tidskriftsartikel (refereegranskat)abstract This paper reports the fabrication of epitaxial 4H-SiC bipolar junction transistors (BJTs) with a maximum current gain beta = 64 and a breakdown voltage of 1100 V. The high beta value is attributed to high material quality obtained after a continuous epitaxial growth of the base-emitter junction. The current gain of the BJTs increases with increasing emitter width indicating a significant influence of surface recombination. This "emitter-size" effect is in good agreement with device simulations including recombination in interface states at the etched termination of the base-emitter junction.
24.	Domeij, Martin, et al. (författare) Current gain of 4H-SiC bipolar transistors including the effect of interface states 2005 Ingår i: Materials Science Forum. - ZURICH-UETIKON : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. - 0878499636 ; 483, s. 889-892 Tidskriftsartikel (refereegranskat)abstract The current gain (β) of 4H-SiC BJTs as function of collector current (I-C) has been investigated by DC and pulsed measurements and by device simulations. A measured monotonic increase of β with I-C agrees well with simulations using a constant distribution of interface states at the 4H-SiC/SiO2 interface along the etched side-wall of the base-emitter junction. Simulations using only bulk recombination, on the other hand, are in poor agreement with the measurements. The interface states degrade the simulated current gain by combined effects of localized recombination and trapped charge that influence the surface potential. Additionally, bandgap narrowing has a significant impact by reducing the peak current gain by about 50% in simulations.
25.	Domeij, Martin, et al. (författare) Dynamic avalanche and trapped charge in 4H-SiC diodes 2000 Ingår i: SILICON CARBIDE AND RELATED MATERIALS. ; , s. 1327-1330, s. 1327-1330 Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract A dynamically reduced breakdown voltage from more than 2 kV under static conditions to 300 V during reverse recovery was measured for 4H-SiC p(+)nn(+) diodes. Device simulation indicates that deep hole-trapping donors in the n-base, close the pn junction, could explain the dynamically reduced breakdown voltage. Hole traps situated 0.66 eV above the valence band were found in the diode n-base by DLTS measurements.

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