Silicon Carbide and Related Materials 2004

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Authors: Mykola S. Boltovets, Volodymyr V. Basanets, Nicolas Camara, Valentyn A. Krivutsa, Konstantinos Zekentes
Abstract: The switching characteristics of 4Н-SiС p-i-n diodes with 6 µm long i-region were investigated in the 20÷500 °С temperature ranges. It is shown that the diode reverse current increases with temperature and does not exceed 10-7 А at temperature of 500 °С (UR = 100 V). The diode resistance rF at forward current of 40 mA decreases as temperature increases from 20 up to 500 °С. The effective minority charge carrier lifetime in the i-region (τр) was determined from the diode switching (from forward current to reverse voltage) characteristics; it was about 5 ns. As temperature increases from 20 up to 500 °С, τр increases by a factor of 3. We discuss the possibility of application of such diodes (i) in microwave switching facilities and (ii) as temperature sensors. A comparison is made between the parameters of 4Н-SiС p-i-n diodes and those of Si p-i-n diodes with comparable values of calculated blocking voltage.
Authors: Anatoly M. Strel'chuk, Vitalii V. Kozlovski, Alexander A. Lebedev, N.Yu. Smirnova
Abstract: Excess currents of the different nature in 6H-SiC pn structures of the different origin and parameters were investigated. The effect of the suppression of the forward and reverse excess currents were observed after 0.9 MeV electron (dose 5x1016 ÷ 1.6x1017 cm-2) and 8 MeV proton (dose 5x1015 cm-2) irradiation for structures with shunts which is probably due to the presence of relatively small inhomogeneities. The shunts in another group of pn structures probably are more high capability and they are more stable against degradation during irradiation.
Authors: Pierre Brosselard, Thierry Bouchet, Dominique Planson, Sigo Scharnholz, Gontran Pâques, Mihai Lazar, Christophe Raynaud, Jean-Pierre Chante, Emil Spahn
Abstract: Overcoming the physical limits of silicon, silicon carbide shows a high potential for making high voltage thyristors. After a simulation based optimization of the main thyristor parameters, including JTE protection and a SiO2 layer passivation, 4H-SiC GTO thyristors were realized and characterized. Designed for a theoretical blocking capability of nearly 6 kV, the electrical characterization of all device structures revealed a maximum blocking voltage of 3.5 kV. Comparing simulation and measurement suggests that a negative oxide charge density of ~ 2×1012 cm-2 causes the decrease in electrical strength.
Authors: Phillippe Godignon
Abstract: Silicon Carbide has proven its strong interest for power and high frequency devices but it also has superior characteristics for application in the sensors and MEMS fields. The characteristic requirements of the starting material are different from that of power devices since the level of defects is not so critical while the layer stress is important especially in 3C-SiC on Si. The keyprocess for MEMS fabrication is the etching, which is progressing thanks to ICP process improvements. A perfect control of the etching step could allow the obtention of nano-resonators in SiC with fairly superior characteristics to the Si ones. Other electrical sensors for high temperature application such as gas sensors or Hall sensors have been also successfully developed taking profit of the deep etching process improvement and high temperature contact developments.
Authors: Giuseppe Bertuccio, Simona Binetti, S. Caccia, R. Casiraghi, Antonio Castaldini, Anna Cavallini, Claudio Lanzieri, Alessia Le Donne, Filippo Nava, Sergio Pizzini, L. Rigutti, G. Verzellesi
Abstract: High performance SiC detectors for ionising radiation have been designed, manufactured and tested. Schottky junctions on low-doped epitaxial 4H-SiC with leakage current densities of few pA/cm2 at room temperature has been realised at this purpose. The epitaxial layer has been characterised at different dose of radiations in order to investigate the SiC radiation hardness. The response of the detectors to alpha and beta particle and to soft X-ray have been measured. High energy resolution and full charge collection efficiency have been successfully demonstrated.
Authors: Francesco Moscatelli, Andrea Scorzoni, Antonella Poggi, Mara Bruzzi, Stefano Lagomarsino, Stefano Mersi, Silvio Sciortino, Mihai Lazar, Annalisa Di Placido, Roberta Nipoti
Abstract: Silicon carbide is a promising wide-gap material because of its excellent electrical and physical properties, which are very relevant to technological applications. In particular, silicon carbide can represent a good alternative to Si in applications like the inner tracking detectors of particle physics experiments [1]. In this work p+/n SiC diodes realized on a medium doped (1×1015 cm -3), 40 µm thick epitaxial layer are exploited as detectors and measurements of their charge collection properties under beta particle radiation from Sr90 source are presented. Preliminary results till 900 V reverse voltage show a good collection efficiency of 1700 e- and a collection length (ratio between collected charges and generated e-h pairs/µm) equal to the estimated width of the depleted region.
Authors: Nikita B. Strokan, Alexander M. Ivanov, N.S. Savkina, Alexander A. Lebedev, Vitalii V. Kozlovski, Mikael Syväjärvi, Rositza Yakimova
Abstract: Nuclear-particle detectors based on SiC with a structure composed of an n+-type substrate, a p-type epitaxial layer, and a Schottky barrier are studied. Structures with a ~10-µm-thick 6H-SiC layer exhibit transistor properties, whereas those with a ~30-µm-thick 4H-SiC layer exhibit diode properties. It is established that a more than tenfold amplification of the signal is observed in the transistor-type structure. The amplification is retained after irradiation with 8-MeV protons with a dose of at least 5 × 10 13 cm –2 ; in this case, the resolution is ≤ 10%. Amplification of the signal was not observed in the structures of diode type. However, there were diode-type detectors with a resolution of ≈ 3%, which is acceptable for a number of applications, even after irradiation with the highest dose of 2 × 10 14 cm.
Authors: Alexander M. Ivanov, Evgenia V. Kalinina, G. Kholuyanov, Nikita B. Strokan, G. Onushkin, Andrey O. Konstantinov, Anders Hallén, Andrej Yu. Kuznetsov
Abstract: The spectrometric characteristics of the detectors based on 4H-SiC using 4.8-7.7 MeV a-particles were determined. The Cr Schottky barriers with areas of 1×10-2 cm2 were performed^by vacuum thermal evaporation on 4H-SiC epitaxial layers grown by chemical vapor deposition (CVD) with thickness 26 and 50 µm. The concentrations of the uncompensated donors into CVD epitaxial layers were (6-10) ×1014 cm-3, that allowed to develop a detector depletion region up to 30 µm using reverse bias of 400 V. The energy resolution less than 20 keV (0.34%) for lines of 5.0- 5.5 MeV was achieved that is twice as large of the resolution of high-precision Si-based detectors prepared on specialized technology. The maximum signal amplitude of 4H-SiC - detectors corresponding to the average electron-hole pair generation energy was found to be 7.70 eV.
Authors: A. Trinchi, W. Wlodarski, G. Faglia, A. Ponzoni, E. Comini, G. Sberveglieri
Abstract: Silicon carbide based metal-oxide-semiconductor (MOS) devices are attractive for gas sensing in harsh, high temperature environments. We present a hydrocarbon gas sensor based on a Pt–thin Ga2O3–SiC device. This sensor has been employed as a Schottky diode, and is capable of operating at temperatures around 600°C. Exposure to propene (C3H6) gas results in shift towards lower voltages in the current-voltage (I-V) characteristic curve, as well as a change in series resistance of the diode. The Ga2O3 thin films were prepared by the sol-gel process and deposited onto the SiC by spin coating. The Pt layer was deposited on the top of the Ga2O3, forming the Schottky contact. It also serves to dehydrogenate the hydrocarbons. The sensors responses were stable and repeatable towards propene at operating temperatures between 300 and 600°C. In this paper the effect of biasing is investigated by analyzing the output voltage of the diodes when biased at different constant currents.
Authors: Enn Velmre, Andres Udal, Mihhail Klopov
Abstract: The strength of recombination radiation reabsorption in GaN is discussed. For material comparisons a distance-dependent radiative recombination transfer function F(u) is introduced. In spite of high absorption rates of GaN, calculations predict ca. one order of magnitude higher photon recycling efficiency in GaN than in GaAs. Simulations of 2H-GaN p −i −n structures predict appearance of S-shaped forward I/V characteristics due to the generation of extra carriers in the base center. The study of GaN bipolar transistors shows that the radiative recombination will reduce the carrier lifetimes in the base and thereby restrict essentially the achievable current gains.

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