Study of optical sensors of the form Al/a-SiC:H/c-Si(n) with high sensitivity

In the present work optical sensors of the form Al/a-SiC:H/c-Si(n), for different thickness of a-SiC:H thin films are studied. More specifically, a-SiC:H thin films were deposited by rf sputtering technique on c-Si(n) substrates for different thickness of the amorphous semiconductor and, subsequently, the samples were annealed in the temperature range from 300C up to 675 C. Experimental measurements of the optical response of these sensors showed that for thicknesses of a-SiC:H greater than a critical value, which depends on annealing temperature, a mechanism of losses is appeared in the region of wavelengths from 525nm up to 625nm. This behaviour is attributed to the recombination of photo-generated electrons-hole pairs in the neutral region of a-SiC:H, when this exceeds the diffusion length of minority carries, Lp. Also, the value of the reverse bias voltage appears to influence considerably the optical response of these sensors when d > Lp in the case where the a-SiC: H thin films were annealed at 600C.