Free carrier optical absorption used to analyze the electrical properties of polycrystalline silicon films formed by plasma enhanced chemical vapor deposition

Ž. The electrical properties of 400 oriented polycrystalline silicon films fabricated at 300C by 100-MHz plasma enhanced chemical vapor deposition from gaseous mixture of SiF H SiH are reported. A double layered structure of phosphorus-doped 42 4 Ž. poly-SiHF film 200 nm undoped poly-SiHF film was adopted to research the changes in electrical properties in the doped layer induced by the undoped layer thickness. The carrier mobility in the crystalline grain of the doped layer, analyzed by free carrier optical absorption, increased from 10 to 35 cm 2 Vs as the undoped film thickness increased from 0 to 1000 nm. The carrier density in the crystalline grain was 2.5 10 20 cm 3 for each sample. The grain properties in the doped layer improved as the undoped film thickness increased. 2001 Elsevier Science B.V. All rights reserved. Ž.