AVS 47th International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuP

Paper TF-TuP28
Microstructure and Optoelectronic Properties of a-SiGe:H Thin Films Fabricated by the Low Frequency (55 kHz) Glow Discharge

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: A.A. Aivazov, UniSil Corp.
Authors: B.G. Budaguan, Moscow Institute of Electronic Technology, Russia
A.A. Sherchenkov, Moscow Institute of Electronic Technology, Russia
G.L. Gorbulin, Moscow Institute of Electronic Technology, Russia
A.A. Berdnikov, Moscow Institute of Microelectronics of Russian Academy of Science, Russia
V.D. Chernomordic, Institute of Microelectronics of Russian Academy of Science
A.A. Aivazov, UniSil Corp.
Correspondent: Click to Email
The incorporation of Ge in a-Si:H allows to decrease the optical band gap which is necessary for a different optoelectronic applications such as infrared sensors, solar cells, etc. However the increase of Ge content leads to the increase of defects and to the deterioration of the electronic properties. So, the development of the appropriate fabrication technology of a-SiGe:H films is essential. We have shown that a-Si:H films with high electronic properties can be fabricated with using of low frequency (55 kHz) glow discharge. In this work we deposited a-SiGe:H for the first time by this method and investigated the growth mechanism, microstructure and optoelectronic properties of the layers. The a-SiGe:H films were fabricated at different germane content from 0 to 44.5%, and substrate temperatures, T@sub s@, from 175 to 275 °C. It was shown that the high deposition rate of a-SiGe:H is caused by an increased flux of radicals to the growth surface due to the close position of the radical generation region to the electrode. The joint analysis with using of infrared and atomic force microscopy showed that a-SiGe:H films have an island type morphology. The measurements of optoelectronic properties indicate that the decrease of the E@sub g@ with the increase of GeH@sub 4@ is determined by the increase of the concentration of Ge-Si bonds in the interior of islands, while the Si-H@sub n@ and Ge-H@sub n@ bonds are clustered on the island surfaces and does not affect the optical bandgap. The modeling of the photoconductivity showed that density of states distribution does not significantly change with the decrease of T@sub s@. Small decrease of photoconductivity accompanied by large decrease of dark conductivity leads to the high values of photosensitivity at lower temperatures for a-SiGe:H with E@sub g@ as low as 1.5 eV. Thus, 55 kHz glow discharge method allows to fabricate device quality low band gap a-SiGe:H films at low T@sub s@ and high deposition rate.