Optimization of the electrical properties of Al/a-SiC:H Schottky diodes by means of thermal annealing of a-SiC:H thin films

Abstract

The present work reports on the optimization of the electrical properties of Al/a-SiC:H Schottky diodes by means of thermal annealing of a-SiC:H thin films. Optical transmission experiments have shown that the optical properties of the films are affected by thermal annealing when Ta>600°C, due to emission of hydrogen bonded to silicon. Although the electrical properties of Al/a-SiC:H Schottky diodes are invariant for Ta⩽400°C, for higher Ta these properties are improved with the optimum result achieved at Ta=600°C. At this annealing temperature the linear logI–V characteristics span about eight orders of magnitude and the ideality factor is 1.09±0.04, making these diodes very interesting for many potential applications. For higher Ta (>600°C) the electrical properties of Al/a-SiC:H Schottky diodes deteriorate with complete degradation at Ta=700°C. For temperatures up to 600°C this behavior is attributed to relaxation of the strain in the amorphous network which is possibly combined with weak hydrogen emission for temperatures up to 600°C, leading to an optimum material quality. For further increase of Ta (>600°C) the observed deterioration of the electrical properties of Al/a-SiC:H Schottky diodes is due to the intensive emission of hydrogen atoms bonded to silicon that cause voids in the amorphous network. These results are also supported by the experimental values of the room temperature apparent barrier height of the Al/a-SiC:H junction φbRT and its temperature coefficient γ.