Temperature-dependent interface reactions and electrical contact properties of titanium on 6H-SiC
n this study the system Ti-Si-C was investigated
in terms of two aspects, metallurgical and electrical, in order to understand
the formation and the properties of Ti electrical contacts on n-type 6H-SiC.
For the metallurgical investigation bulk diffusion couples were prepared from
monocrystalline 6H-SiC and Ti and annealed between 700 and 1200 degrees C for
different lengths of time. The reaction zones were investigated using a SEM
(secondary electron and backscattered electron images as well as
energy-dispersive X-ray analysis). For the investigation of the electrical
properties Ti contacts were sputter-deposited onto 6H-SiC wafer stripes and
annealed at similar temperatures. The contact properties were measured in terms
of current-voltage characteristics. We discovered that, over the whole
temperature range investigated, the reaction layer growth follows a parabolic growth
law which is thermally activated. Above 1200 degrees C the diffusion path from
SiC to Ti is SiC/Ti3SiC2/Ti5Si3/two-phase Ti5Si3+TiC1-y/Ti5Si3/Ti. The contacts
show ohmic behaviour. Between 1000 and 800 degrees C the diffusion path is:
SiC/Ti3SiC2/Ti5Si3/two-phase Ti5Si3+TiC1-y/Ti3Si/Ti. The contacts are also
ohmic. Below 700 degrees C the diffusion path is SiC/TiC1-y/two-phase
Ti5Si3+TiC1-y/Ti3Si/Ti. The contacts are of Schottky type. It is concluded that
the phase in contact with the SiC determines the electrical properties of the
junction and the possibility of manufacturing a complete Schottky diode using
n-type 6H-SiC and Ti only is demonstrated.
Source:IOPscience
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