Papers by Keyword: Minority Carrier Diffusion Length

Abstract: Minority carrier diffusion lengths were measured for the set of n- and p-type silicon samples with NiSi2 precipitates of different electronic structure. We found that the type of precipitate electronic states in the upper part of band gap had no influence on the recombination activity of NiSi2 precipitates. Minority carrier diffusion length L was found to be related to the precipitate density N and L ~ 2 × N -1/3 for n-type Si samples and L ~ 1 × N -1/3 for p-Si samples. Hydrogenation of the p-type Si sample with nanoscale nickel silicide precipitates resulted in an increase of the L value up to a factor of 3, while in n-Si L remained practicaly the same. The only hole emission in the samples of both conductivity types was detected in MCTS measurements and the cross section for the hole capture with the electronic states of the precipitaes was estimated to be as large as 10-11 cm-2.

Abstract: This paper presents results of investigations about the influence of Hydrogen (introduced by annealing or plasma implantation), and Helium (ion implantation followed by a proper annealing for creating nanocavities) on the electrical properties of 4H-SiC n-type epitaxial samples. First, 4HSiC epitaxial layers were hydrogenated either by annealing under H2 ambient or by a RF plasma treatment. This last process took place before or after the deposition of Schottky contacts. Two different annealing temperatures were imposed (300°C and 400°C), as well as two plasma hydrogen doses for the same low energy. An improvement of electrical characteristics (25 % increasing of the minority carrier diffusion length, lowering of ideality factor, better switching characteristic) is detected for samples annealed at 400°C. The treatment of 4H-SiC surface in hydrogen plasma through Ni metal also increases the diffusion length, but not sufficiently to have an effect on I-V characteristics. A second set of 4H-SiC epitaxial layers were secondly implanted with He+ ions at two distinct temperatures. An annealing at 1700°C during 30 minutes under argon atmosphere was then carried out. C-V measurements revealed the presence of a high charge density zone around the nanocavities, containing fixed negative charges, opposite in sign to the donor atoms.

Abstract: The epitaxial growth of SiC by a hot-wall CVD system using monomethylsilane (CH3SiH3) as a precursor is described. In the case of CH3SiH3 source only, an undoped homoepitaxial layer showed an n-type conduction around 1016-1017cm-3 on the Si face. To improve the quality of epilayers, the simultaneous supply of CH3SiH3 and C3H8 was carried out. The pit density of grown layers was reduced from 105 to 103cm-2, and a donor concentration as low as 1.6×1014cm-3 was achieved. An attempt to increase of the growth rate was also investigated.

Abstract: Propagations of dislocations in 4H-SiC were evaluated three-dimensionally by a planar mapping EBIC method with the control of accelerating voltages. Screw dislocation (SD), edge dislocation (ED), and basal plane dislocation (BPD) were clearly observed through the 20nm-thick Ni Schottky contact on SiC. From the analysis of BPD extended on {0001}, the intensity of EBIC signals was proportional to the depth position of defect. In addition, the information of the decomposition and combination for dislocations can be obtained from the fluctuation of EBIC signal along the scanning position.