The ITO films are used in wide range of optoelectronic applications and are of growing importance in the electronic device fabrication. One of the possible applications of ITO films is in the newly designed vertical cavity surface emitting lasers (VCSEL) .
This research were focused on the deposition technology of ITO films, which are intended to be used in VCSEL lasers emitting in 1000 nm band fabrication technology. The ITO films should have high transmission (above 85%), low resistivity (about 10-4 Ωcm) and smooth surface to allow for deposition of dielectric Bragg reflectors.
In this work there was examined the influence of parameters of deposition process on optical and electrical parameters of ITO films. The films were deposited using the dc magnetron sputtering system. With the ITO film thickness 200 nm the subsequent annealing steps were done in the air atmosphere in 500oC. Spectral characteristics were measured in the 400-1100 nm range. Optical constants n, k were determined with the spectroscopic ellipsometer and surface smoothness was tested with the AFM use.
As deposited ITO transmission for the 1000 nm wavelenght was in the 60% - 93% range. After annealing the ITO transmission increased to 84-100%. It was observed that the deposition step parameters strongly affect electrical resistivity of the ITO films. After annealing of the ITO films the resistivities of all sample decreased to tens μΩcm.
The refractive index of ITO films measured for 1000 nm wave does not depend on the partial pressure of argon and oxygen, but depends on the deposition rate.
In conclusion, we have elaborated stable technological conditions of the ITO films with satisfactory optical and electrical properties for optoelectronic applications.
1. A. Szerling, D. Wawer, K. Hejduk, T. Piwonski, A. Wojcik, B. Mroziewicz, M. Bugajski: Reflectance study of SiO2/Si3N4 dielectric Bragg reflectors. Optica Applicata, Vol. XXXII, No. 3, 2002