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

Abstract

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 300°C 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 600°C. © 2008 Kavala Institute of Technology.