An Ellipsometric Measurement of Optical Properties for InP Surfaces

Several chemical cleaning procedures for InP surfaces have been studied using ellipsometry. The strong influence of cleaning on the optical properties of InP surfaces suggests that the measurements involve the formation of surface films. In order to determine the complex index of refraction for InP , a novel method which employs ellipsometry measurements of a thin nonabsorbing film on a substrate rather than measurements of a bare surface has been explored. From the knowledge of the refractive index for a series of thicknesses of films on a substrate, the complex refractive index value for the substrate can be determined. Plasma enhanced chemical vapor deposition (PECVD) SiO 2 and Si 3 N 4 films on InP have been used for this experiment, and the complex refractive index for InP has been determined to be 3.521 + i 0.300 at the wavelength of 632.8 nm.