Characterization of amorphous silicon carbide and its application to contact barrier diode

Thin films of amorphous silicon carbide were prepared using Polymer-Source Chemical Vapor Deposition (PS-CVD) at temperatures between 750 and 1000°C. The substrates were silicon single crystal wafers of p-type and n-type, and thermally-grown silicon dioxide substrates. The chemical and electrical properties of the films were studied by various techniques, including Fourier-transform infrared spectroscopy, Elastic Recoil Detection (ERD), and capacitance-voltage technique. A correlation was observed between the average concentration of oxygen in the films and the deposition temperature, linking a low oxygen concentration in the film to a high deposition temperature. However, the concentration of oxygen in the films deposited at the same temperature was independent of the substrate. The thin films deposited at low temperature showed insulating behaviour, while the semiconducting behaviour was obtained at high deposition temperatures. Ohmic contacts were obtained on the deposited a-SiC thin film by evaporating nickel contacts, followed by annealing of the sample at 800°C for 2 minutes. The average Hall mobility was found about muH = 34 cm 2/V.s for the samples deposited on SiO2 substrate at 1000°C.;The general characteristics of wide band gap a-SiC deposited at 750°C, was studied using aSiC/c-Si heterostructures applied as the contact barrier diodes. The current transport properties of a-SiC thin film deposited on a p-type silicon c-Si substrate were investigated using current-voltage (IV) and capacitance-voltage (CV) measurements. IV characteristics showed an exponential dependence of current to the applied voltages for low forward bias while the space charge limited current characteristics dominated for higher forward bias. CV characteristics indicated a p-type property for a-SiC which is resulted by the injected positive charge from p-type silicon substrate. The hole mobility and injected carrier lifetime in a-SiC thin film was calculated using a model of space-charge limited current. The variation in effective hole mobility of a-SiC, which was ranged between 10-4 and 10 -7, was attributed to the various values of defect density of the a-SiC thin films.