Papers by Keyword: Miniband

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Authors: Jörg Pezoldt
Abstract: Based on a Kronig-Penney model the electronic properties of heteropolytypic superlattices consisting of lamellas of 3C-and 4H-SiC polytypes with thicknesses below ten nanometers are analysed. Due to the large difference in the electron negativity and the resulting high barriers between the different polytypic lamellas an increased number of minizones compared to other materials are formed. The field strength for the appearance of the negative differential resistance in the heteropolytypic superlattice is lower than the critical fields in the silicon carbide polytypes.
278
Authors: Vladimir Ilich Sankin, Pavel P. Shkrebiy, N.S. Savkina, Alla A. Lepneva
661
Authors: Vladimir Ilich Sankin, Alexander V. Andrianov, A.G. Petrov, P.P. Shkrebiy, A.O. Zachar'in
Abstract: We report on efficient terahertz emission in the region of 1.5-2 THz from high electric field biased 6H-SiC structures with a natural superlattice at liquid helium temperatures. The shape of the emission spectrum, the linear dependence of its maximum on the bias and the characteristic field strength required to achieve the emission allow the emission to be attributed to steady-state Bloch oscillations of electrons in the SiC natural superlattice.
553
Authors: Vladimir Ilich Sankin, Pavel P. Shkrebiy, Alexey N. Kuznetsov, N.S. Savkina
1407
Authors: Vladimir Ilich Sankin, Andrey M. Monakhov, Pavel P. Shkrebiy
Abstract: In the 6H-SiC p+-n--n+ junction the effect of the premature breakdown has been revealed. This effect stimulated by the small temperature increase and illumination by light with energy greater than the bandgap energy of 6H-SiC. The breakdown field appears to be 20% less than the intrinsic breakdown field in these structures.
431
Authors: Vladimir Ilich Sankin, Pavel P. Shkrebiy, Alla A. Lepneva, M.S. Ramm
Abstract: A natural superlattice (NSL) in silicon carbide polytypes is shown to introduce a miniband structure into the conduction band, which leads to a number of effects in phenomena of quantum-mechanical transport and impact ionization when the electric field directed along an axis of NSL (axis C in crystal). These processes are absolutely traditional when the electric field is perpendicularly to this axis. The parallel field phenomena are explained by the effects of the Wannier–Stark localization (WSL) among them the Bloch oscillations effect is most prominent today.
513
Authors: Vladimir Ilich Sankin, Pavel P. Shkrebiy, Alla A. Lepneva, Andrey G. Ostroumov, Pavel L. Abramov
Abstract: A natural superlattice (NSL) in silicon carbide polytypes is shown to introduce a miniband structure into the conduction band, which leads to depressing of the electron impact zone-zone ionization at 300K with the electric field directed along the crystal axis or the NSL axis. The NSL influence can be also observed in the nitrogen impact ionization at 4.2K. In this case for the parallel field the impurity breakdown has not been fixed up to the fields 1.6 MV/cm in 6H-SiC. These results are explained by the insufficient gain in miniband for the ionization electron energy. Therewith the impurity breakdown at the electric field perpendicular to this axis correlates with a classical picture.
209
Authors: Vladimir Ilich Sankin, Alexander V. Andrianov, A.G. Petrov, A.O. Zachar'in, Sergey S. Nagalyuk, Pavel P. Shkrebiy, Alexander A. Lebedev
Abstract: Recently the intense terahertz electroluminescence from monopolar n++–n –n+ structures of 6H- and 8H-SiC of natural superlattices at helium temperatures due to Bloch oscillations was discovered. In the present work we present the THz emission spectra of bipolar n++–π–n+ structures (π is a high-resistance layer of p-type conductivity) of natural superlattices 4H-, 8H- and 15R-SiC at 7 K. The bipolar n++–π–n+ structures of 4H- and 8H-SiC were analogous to those of structures for which the negative differential conductivity effect was observed earlier for three polytypes (4H, 6H and 8H) at T=300 K. We demonstrate resemblance and differences of the spontaneous THz emission spectra for the monopolar and bipolar 4H-, 6H- 8H- and 15R-SiC natural superlattices caused by Bloch oscillations of electrons in the SiC natural superlattice.
310
Authors: Vladimir Ilich Sankin, Rositza Yakimova
Abstract: The work deals with the highly important problem of the qualitative temperature dependence of avalanche breakdown voltage in p-n junctions based on 4H-SiC. As it has been shown before, the temperature coefficient of avalanche breakdown voltage (TCABV) is negative in seven SiC polytypes, including 4Н-SiC. This effect has been explained by the Wannier-Stark localization (WSL). It is worth noting that the plane of the investigated p-n junctions coincided with the basal plane (0001). However the current SiC device technology prefers 4H-SiC p-n junction formation on a plane that has 8о disorientation from (0001). This may result in a weakening of the WSL and, correspondingly, in a positive TCABV. This problem has been elucidated in the present paper. The photocurrent of 4H-SiC p-n junctions in a strong electric field has been scrutinized, that has allowed to discover a negative differential conductivity region and it has testified to the WSL process and negative TCABV.
707
Authors: Vladimir Ilich Sankin, Pavel P. Shkrebiy, Alexander A. Lebedev
Abstract: The dependence of short-circuit photo-current on the voltage applied to the source-gate (or drain-gate) junction Vg was studied. One should consider the fact that the photo-current begins to drop with voltage exceeding certain threshold value. Thus the 6H-SiC JFET behaves uncommonly. Moreover Isd ~Vg dependence shows a drop Isd to zero at a condition that there is a non-pinched-off part of the channel. For a comparison parallel investigations were conducted with two industrial Si JFETs with a structure similar to that of 6H-SiC JFET under study. The results obtained for Si JFETs are trivial for photocurrent and Isd. We believe that the effects observed in 6H-SiC JFET should be attributed to the Wannier-Stark localization regime.
873
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