Papers by Keyword: Al-Ti Composite

Abstract: The dependence of the structure and composition of nanolayered Au/Ti/Al ohmic contacts to p-type 4H-SiC on the initial Ti:Al ratio has been investigated. Two contact compositions, Au/Ti(70%)/Al(30%) and Au/Ti(30%)/Al(70%), have been studied regarding the electrical properties, structure, composition and annealing temperature in the interval 850 – 1000o C. The correlation between the electrical behaviour and structure of the annealed contacts is discussed. Very low resistivity of 1.42x10-5 .cm2 after annealing at 900o C has been obtained for the contact having an initial composition Ti:Al (30:70), while the lowest resistivity of 1.21x10-5 .cm2 has been measured for the contact with a composition Ti:Al (70:30) after annealing at 1000o C. Strong dependence of the contact structure on the Ti:Al ratio and annealing temperature, respectively, has been found out. A presence of two phases, Au2Ti and Al3Ti, in all contacts has been determined after annealing, despite the temperature value and Ti:Al ratio. The TEM analysis reveals that titanium and aluminum silicides and carbides are formed after annealing as the Ti:Al ratio affects the kind of silicides and carbides created. It is obtained that the initial composition of the deposited metal layers influences only the phase composition of the annealed contact but not the grain sizes of the dominant phases formed. The origin of the ohmic properties improvement is explained by the formation of Ti3SiC2 compound and/or enhanced carrier transport by the presence of metal spikes into SiC depending on the initial contact composition and as consequence the optimal annealing temperature.

Abstract: Electrical, morphological and chemical properties of nanolayered Au/Ti/Al ohmic contacts with different Ti:Al ratio are investigated. Contact resistivities of 1.42×10-5 ⋅cm2 and 1.21×10-5 ⋅cm2 are achieved for Au/Ti(70)/Al(30) and Au/Ti(30)/Al(70) contacts, respectively. It is found that the Ti:Al ratio does not affect the lowest resistivity value but influences on the optimal annealing temperature at which it is obtained. The different optimal annealing temperature provokes different element distributions and interface chemistry of the annealed contacts. An increase of the Al concentration in the contact composition causes essentially the surface morphology leading to an increase in surface roughness of the as-deposited and annealed contacts.