Optimization of Al/a-SiC:H optical sensor device by means of thermal annealing

The optimization of optoelectronic properties of Al/a-SiC:H Schottky diodes grown as Al/a-SiC:H/c-Si(n) structures is studied by means of thermal annealing of a-SiC:H thin films. According to the spectral response of the Schottky diodes the measured quantum efficiency, η_measured, increases with increasing annealing temperature (400–600 °C), whereas η_measured decreases for T_a>600 °C. For T_a=600 °C, optimum material quality of a-SiC:H films is achieved and the spectral response of the Al/a-SiC:H/c-S(n) structures present very high and almost constant values (η_measured80%) for the whole range of wavelengths from 500 up to 850 nm. These results show that our Al/a-SiC:H/c-S(n) structures can be very attractive as optical sensors. Diffusion length calculations as well as the mobility by lifetime product (μτ)_p of the minority carriers (holes) of a-SiC:H films present a dependence on T_a similar to that of the measured quantum efficiency. Finally, the quantum efficiency of films processed with T_a=675 °C is found to increase when the Al/a-SiC:H/c-S(n) structures are exposed to hydrogen, a result that could be promising for the construction of a hydrogen detection sensor.