AVS 47th International Symposium
    Semiconductors Wednesday Sessions
       Session SC+EL+SS-WeA

Paper SC+EL+SS-WeA8
Electrical and Optical Properties of Silicon : Germanium Alloys prepared by DC Magnetron Sputtering

Wednesday, October 4, 2000, 4:20 pm, Room 306

Session: Semiconductor Alloys
Presenter: A. Subrahmanyam, Indian Institute of Technology, Madras, India
Authors: A. Subrahmanyam, Indian Institute of Technology, Madras, India
S. Karthikeyan, Indian Institute of Technology, Madras, India
J. Asbalter, Indian Institute of Technology, Madras, India
P. Amirtharaj, National Institute of Standards and Technology
Correspondent: Click to Email
The Silicon: Germanium (Si:Ge) alloys are being used in various semiconductor devices. As is well known, these alloys offer advantages in band gap engineering, and can integrate well with the existing silicon technology. Several studies have been made on these alloys. In the present paper, we report the electrical and optical properties of Si:Ge alloys prepared by DC Magnetron sputtering technique. A 7.5 cm diameter circular magnetron cathode has been designed and fabricated. The balanced magnetron cathode is operated at low pressures (4.0 x 10@super -3@ mbar). Argon is the sputter gas. The target is prepared by bonding commercially available Silicon wafer to the water cooled copper backing plate. A small portion of the erosion area on the magnetron cathode is covered with pure germanium wafer. The alloys of Si:Ge (undoped) are prepared (at room temperature 25°C) on glass and Si substrates. The growth parameters in the present study are : flow rate of argon (180 - 250 sccm), Magnetron power (80 - 225 watts) and germanium content in the alloy. The thickness and refractive index of the films is measured by ellipsometer in the wavelength range 300 - 700 nm. The thickness of these alloy films is about 150 nm. The alloy films have been found to be amorphous. The germanium content in the alloy films is varied between 15 - 30 atomic % and is estimated by EDAX and RBS analysis. The optical absorption and photo conductivity measurements have been made on these alloys. The optical band gap of these alloys is in the range 1.45 - 1.6 eV. The dark conductivity is in the order 10@super-@ mho cm@super-1@. The deposition rate is observed to be linear with the magnetron power till 120 watts.