SIMULATION AND FABRICATION OF GE ISLANDS ON SI METAL-SEMICONDUCTOR-METAL PHOTODETECTORS

Presenter	:	HADI MAHMODI SHEIKH SARMAST
E-mail	:	-
Date	:	1 / 10 / 2010
Time	:	3.00 PM
Venue	:	PHYSICS MEETING ROOM LEVEL 2, SCHOOL OF PHYSICS
Sypnosis	:	In this thesis, experimental fabrication and theoretical simulation of Ge islands Si based metal-semiconductor-metal photodetectors have been reported. Radio frequency (RF) sputtering was used to deposit Ge thin films on silicon substrates. This is followed by rapid thermal annealing (RTA) to form Ge islands. Not only that the annealing produces Ge islands but also wetting layer. The size and density of the islands are greatly influenced by the annealing time. An estimation of the island density shows that it increases from around 0.36 × 109 cm−2 to 1.0 × 109 cm−2 while the average size of the islands decreases from 0.6 μm to 0.1 μm when annealing time increases from 30 s to 60 s at 900 ˚C. Using these samples, metal–semiconductor–metal (MSM) photodiodes were fabricated for small and large islands. The performance of MSM devices were evaluated by dark current, photocurrent and current gain (the ratio of photocurrent to dark current) measurements at room temperature (RT). The presence of Ge islands and wetting layer structure has been shown to provide benefits for Si based MSM photodetectors; reducing the dark current and enhancement of current gain. Simulations of the Ge islands and wetting layer in MSM photodetectors have been performed to verify the experimental results using device simulator ATLAS in Silvaco in this thesis. Simulation results confirmed experimental results. A more detailed simulation studies has been conducted including electron-hole current, electric field, current flow, transient and spectral responses. Hole current dominated the carrier in the Ge layers and device without wetting layer between the fingers shows the best transient response.

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