| dc.description.abstract | In order to improve the performance of optoelectronic devices, reducing the dark current has become one of the important targets for the development of them, and a good passivation layer could effectively function. However, the standard of device dark current continuously increases according to the commercial demand. For the sake of improving the effect of passivation layer, some research groups have deposited double layers of dielectric material as compound films and tried to gain better performance than single layer films.
First of all, we grew some thin films which materials are commonly used as passivation layers. Then we discussed the passivation effect of those films and learned that Si3N4/SiO2 compound films have the best performance. The measured minority carrier lifetime is 584.2 μs and the implied open circuit voltage (iVOC) is 623.2 mV. Next, to enhance the quality of compound films, we grew the SiO2 layer by nitric acid oxidation method instead of PECVD. After the Si3N4 layers has deposited, we annealed the compound films, the maximum of measured lifetime is 1329.7 μs and the iVOC is 646.8 mV at 500℃.
Further, we tried to grow thinner compound films so as to apply them on the Si-based photodetectors. According to the experiments of devices, the compound film with 1.4 nm SiO2 and 5 nm Si3N4 has the best performance. However, due to the short deposited time of Si3N4 by PECVD, we also grew thick Si3N4 film and reduce its thickness by dry etching. Although the passivation effect is better, yet the performance of device is not.
Finally, the compound films were applied on Si-based MIS photodetector. Compared with the devices without compound film (equivalent to MSM structure), the dark current density decreases from 1.37×10-3 A/cm2@-3 V to 6.96×10-5 A/cm2@-3 V, and the responsivity is 4.61 A/W@-3 V. We also discussed the single and double layer insulator with the same materials which are applied on devices as well. The results show that the performance of Si3N4/SiO2 ones are still the best as expected. | en_US |