Rodrigo Martins

This work presents a comparative study between MIS photodiodes produced using high quality amorphous silicon (a-Si:H), deposited by PECVD at 2Å/s, using 13.56 MHz frequency and polymorphous silicon (pm-Si) deposited at 3Å/s using a 27.12 MHz frequency. The results show that the pm-Si:H outperforms the a-Si:H MIS photodiodes by having a rectification ratio of 107, and photosensitivity at AM1.5 conditions of 107, under 1V reverse bias. Apart from that, the pm-Si:H photodiode presents a higher open circuit voltage and better fill factor than a-Si:H MIS photodiode. These results prove that quality devices can be produced at high growth rates by using pm-Si:H. In this work the photodiode performances were correlated to the films properties, aiming to determine the characteristics responsible for the performances exhibited by the pm-Si:H devices.

This work presents the I-V results of a-Si:H/SiOx/Pd MIS (metal-insulator-semiconductor) structures. The a-Si:H was deposited by non-conventional modified triode PECVD. This new configuration allows the deposition of high quality a-Si:H with a photosensitivity of 106, indicating the presence of low density of defects. Spectroscopic ellipsometry measurements revealed that these films are highly dense and present a very smooth surface so allowing a low defect interface between the Pd and the a-Si:H. As a result, we could make MIS photodiodes with barrier heights of 1.17 eV, which give a high reduction of the reverse dark current, an increase of the signal to noise ratio of 106 and an open circuit voltage VOC = 0.5 V. © 2002 Elsevier Science B.V. All rights reserved.